I think it’s about whether the character is believable. Can you view this character as a real, living person? Are their flaws realistic and do they impact their decisions/actions in a believable way? Are their strengths reasonable? Do they interact with other characters that make sense given their relationship, experience, history, etc.
These are a few traits I love to look for:
1. **Depth:** A well-written character has depth beyond surface-level traits. They have a backstory, motivations, desires, fears, strengths, weaknesses, and contradictions that make them feel like real people. They should be capable of growth and change/learn throughout the story.
2. **Be consistent:** While characters should be complex, their actions, thoughts, and behaviors should be consistent with their already *established* traits, values, and experiences.
3. **Have their own thoughts:** These characters don't always just react or nod to events happening. There are moments where they too take charge and give their own opinions on what they think should happen. It could be a wrong choice, but it's still one they made. We don't have to agree with it, but if they have a reason to do it, it's great.
1. E.g., I don't support mass genocides for a cause, but I also understand why Thanos is written the way he is. He isn't fundamentally cruel; he just doesn't want Titan to repeat.
4. **Moral dilemmas:** Characters with internal conflicts, such as moral dilemmas, emotional struggles, or conflicting desires, are far more compelling and relatable, than a character who's just overly awesome at everything.
5. **External dilemmas:** Characters should also face external challenges and obstacles that test their abilities, beliefs, and resolve. Now, they don't have to go to space and sacrifice their life to stop an alien invasion.
1. Even something as simple "I'll stick to my guns even if it's an unpopular opinion" will do.
6. **Voice:** Let's not have cookie-cutter characters. Each character in a plot should have their own distinct personality shining through.
1. Think of your favorite Power Rangers show, and think of how each character is portrayed. They all wear the same suit, but their personality is what distinguishes them apart.
7. **Growth/Arcs:** Characters should develop and change over the course of the story, whether it's through overcoming obstacles, learning from mistakes, or challenging their beliefs. This is kind of an optional thing for me, since characters can be the same jerks they were, but if I were to read a fic where someone went through a life-altering event, I'd for sure expect them to not be the same as they were before.
8. **Realism/Relatability:** By this, I don't really mean, "well I wouldn't make the same choice if I were them, so they're not relatable/realistic at all". Everyone is different. Characters who evoke empathy and connection from the audience are relatable to me. I may not understand their choices/journey, but if it's important to them, then so be it. I won't relate to the experiences, but I *can* relate to the feelings of frustration, hard work, etc., should I be going on a journey that's important to me.
Well-written characters are just...human. Good or evil, jerk or not, just don't make them cardboard characters with no sense of personality.
>Growth/Arcs
This is a big one for main characters, yes. A side character in three chapters may not have access to enough of the story to do this, but someone you follow for 50k, 100k, whatever words you would expect it.
Personal opinions of course:
At the most fundamental level, a well written character is one who engages the audience and creates emotional responses in the way the author intended.
Everything else is a secondary addition to help guide the kind of character you're trying to make.
Now, for most characters what people mean when they say they're well written, it usually means they're believable, full fleshed out people who don't simply appear to be custom made for the story. This is where I believe your Paul Atreides comes in. Paul Atreides is set up to be this prophet, this ubermensch, the culmination of generations of Bene Gesserit breeding programs and lies. If he went in going "Hell, yeah, that's awesome. Let's fool these rubes, bang some hot desert chicks, kick ass and take names." Then he wouldn't be quite as well written to most people, despite that being a perfectly reasonable response. Repulsive, but if you're telling me you haven't met someone like that, then I'd say you've had a blessed life. But Paul has layers. He is conflicted by the Bene Gesserit lies. He loves the fremen and Chani, he doesn't want to abuse their trust. But he also wants to destroy the Harkonnen's get vengeance for his murdered father, and take his place as duke. And he is drawn to that power of prophecy that he also fears.
In this way, it is three things that make him feel so well written. The first is obvious, all these impulses I've described make sense. The viewer can watch that and nod along going, it is reasonable that they would feel those ways.
The second is more interesting, these feelings are in conflict. It is not enough to have all these layers, if they all point them toward the same direction. He is torn between his love and responsibilities, his desires and duties, his relationships and the culture he has become part of. To quote Faulkner: The only thing worth writing about is the human heart in conflict with itself.
And lastly, the narrative itself is built upon those conflicts. Paul may have all those character traits that I've listed above and more. But if I take Paul, pluck him from Dune and dump him in, I dunno, a palace romcom staring him and Irulan, set after the events of the movie. Then I could change literally nothing about him, and he wouldn't be as well written a character, because the the comedy of him having a meet cute with Irulan has absolutely nothing to do with all that juicy conflict.
So that's one. But, there is another.
There are some characters that are somewhat often scoffed at as being lesser than that first kind, that I fundamentally disagree with. There are characters who do not have many layers, or maybe none at all. They are not always consistent in their characterization. There's little to no internal conflict bubbling up inside them. But what they are, is fun to read about and interesting to engage with. These are your Paddington Bear, Superman, the Joker, Darth Vader in ANH and the Emperor in RotJ after Vader got layers added to him, the Wicked Witch of the West, Captain America, most the Knights of the Round Table. They're your snarky sitcom characters who you just have to sit and watch every week.
These characters tend to have a deep defining characteristic and then are put into situations where that gets revealed over and over again, in interesting ways. And the only way to really pull them off is to be engaging, in whatever way the writer can make work. The jokes got to continuously be on point, the horror has to be consistently disturbing, the nobility must be tested and preserved.
whenever you have a value judgement as "well" or "good" it's gonna be hard to define because it's inherently subjective
I think it's easy to get tempted to define it as "realistic", but I don't think that's really the whole truth. Sometimes realism doesn't feel realistic in fiction. There are people in real life that are very flat and boring or that have motivations that are impossible to understand. And sometimes there are interesting characters in fiction that can't really have a real life equivalent
when people say well written they probably just mean compelling. A character that you get invested in. And that's usually because they have depth and complexity, understandable motivations, they have established history and relationships, and all those things connect with each other in some way. So I guess you could also call it the character being *thoroughly* written, or there has been a lot of effort put in characterization.
but also, some characters do not need to be and should not be complex in order to fill the purpose they serve within a story. I would still consider those characters to be well written, because they are exactly as complex as they need to be. So... yeah. I don't know.
I live and die by the Rule of Three. If you can name three *different* aspects of a character's personality (not appearance, not profession, not role, not relationships) then they have enough depth to be worth being the focus.
One-note characters are boring or comic relief.
Two-notes make good supporting characters, foils, or enemies. People you want the reader to recognize by their words and actions.
But if you're going to follow the character for a while, you need more than "he's a patriot and he's compassionate". I agree with u/waiting-for-the-rain and u/SpartiateDienekes about consistency and layers, especially when paired. A character *cannot* be consistent, if we know nothing about them, their thoughts, their feelings, their wants and needs. Yes, a character could always have an easily-bruised ego or a soft spot for children, but if that never shows up until Chapter 57, it's going to *feel* out of nowhere. The more layers a character has, the more they *can* do that will feel like something they *would* do. u/chshcat mentioned characters being complex, I think we're talking about the same thing.
It is also much easier to write a struggle a character has, when there are competing features that character has. A character is a patriot, but has a soft spot for children. Okay, cool. He finds a couple of starving orphans, in his own country, whose other-country parents just died in the war. Now what does he do? Take away either aspect, and there's no conflict. Now, there is. If nothing else, you can start "putting the layers in order" by having the character show which motivations are more important to them, which personality features are more prominent. What finally gets that strong, silent, stoic character to start screaming in rage? To break down and cry? To smile or laugh?
If you cannot find enough aspects of a character to invent a situation (even if it's not in your work) that would create a conflict between those aspects, *there aren't enough aspects*. Relatable is important, compelling is important, boring is *unforgivable*.
Hopefully you got what you needed out of the well-written posts here and possibly also mine.
Personal opinion, bear in mind that all of these are guidelines not rules and can be broken individually:
1. A well-written character has **something they want**, and they want it badly enough to keep the plot moving. It is *possible* to write a narrative about a passive protagonist who primarily has things happen *TO* him (see: Rincewind from Discworld) and have that plot be clever and fun to read, but it's a challenge.
2. They have **strong beliefs about the world** they live in. Think: Arthur Morgan from Red Dead Redemption, and his feelings about the encroachment of industrialized civilization and the death of an era. Think: Aziraphale and Crowley from Good Omens, and their deeply-held and deeply-conflicted feelings about the roles of Heaven and Hell. These can be moral or political stances, but they don't have to be. They also don't necessarily have to be *right.* A compelling villain should have their own beliefs and justifications!
3. Those beliefs should, at some point in the story, **come into conflict**. Either with the situation, or (even better) with *each other!* We love a deeply-written character who has to struggle to balance their priorities, or reckon with the consequences of their actions. To continue the above example -- Arthur having to come to terms with the reality of the consequences of his wild, free-living "outlaw code" and the way it tends to end in brutal violence done to the people he loves.
4. They should have **enough little details to add depth**. Think about it like a drawing; you can have a really well-proportioned figure sketch, but what makes it come to life is the shading and the detail work. This isn't a substitute for the above three things! For me, a common mark of a beginner writer is that they throw a bunch of quirks (e.g. favorite food, catchphrase, etc.) on top of a mostly-flat character, when it should be the other way around: get your bones right first, then flesh them out.
EDIT TO ADD: this is again a personal opinion, but I try not to think about my characters in terms of strengths and flaws. Any strength can be a flaw, and any flaw can be a strength. A character whose strength is their loyalty, can be swayed by that loyalty to turn a blind eye to awful things done by their loved ones. A cowardly and weak-willed character can be the only one smart enough to run away from an overwhelming threat, and they get the warning out while the heroes with bravado are slaughtered. It's more important to be willing to commit, so that trait both helps *and* hinders them -- a mastermind who meticulously plans every detail should be thrown off and stumble when that plan goes off the rails, not magically turn into an improviser who can perfectly play it by ear.
To me, a well-written character consistently acts based on their internal logic. Even if you don't agree with their motivations (for better or worse), you can understand what makes them tick. They have their own reasoning and their behaviour stems from it naturally.
Don't carry for this being the main style when I read an watch stuff I do love playing around that noggin of there's when they interact with anyone K: series is full of it lol
It's not one thing. It's many that work together.
The character and the story work together. They both make you feel. The character has more to them than what the plot demands of them.
Sometimes well-written means that there are many things that they say that are so undeniably them
They feel real. Like a Person. You feel like you would know them in real life and that they have a distinct personality with flaws, quirks, interests and hobbies.
As someone whose fandom had a lot of writers room turnover, has no show bible establishing how various characters are supposed to go, and who has no continuity editor: its not how they act. The late seasons of my show are running on pure charisma. The actors have it in spades. They’re constantly being given wtf self-contradictory lines, temporary amnesia, sudden and bizarre changes in personality, and somehow they keep you sucked in. The writing was amazing s1-2 and after that its just gets lost and the actors are carrying everything.
I think a well written character needs a consistent personality and motivation. If the world affects them, it can change their motivation (e.g. something matters more to them now, or something happened to traumatize the) but it shouldn’t drastically change their personality. What happens in the changed situation should be something they would do with their same personality.
I think the problem the writers in my show had was that they inherited a show they didn’t want and they wanted to force it to be a different show. They had long term result ideas and they tried to bend the characters to fit their result, not write what the characters would have done in the situation. To do this they rely on all kinds of weird things. They decided they wanted a will-they-won’t-they, so they made character B forget that character A is shit for communication and just sit around passively (writers forgot B is assertive and would just have a conversation) waiting for A to figure out their feelings and tell B using the exact words B wants and not synonyms. They make B legit forget when A actually did say they loved B. They made A break up with C to be with A, then start beating themselves up over having not broken up with C which literally just happened. They had goodie two shoes B try to kill A for reasons no one understands, because they thought it bought them entry into their season plot idea.
There’s so much fake drama and ridiculous soft reboot premises each later season its ridiculous, hence the many rich opportunities for fixits and whatifs. There are a ton of stories that grow out of the many, many cases in which a reasonable fan might ask: what would happen to this part of the story if all the characters behaved as established before the guy who wrote the pilot stopped consulting? Because that’s when characterization started going to Hell.
I think if you have an overarching plot idea and you want to write a good character, you have to listen to them. You either need to sit around like an engineer and figure out what specific things can nudge this character into the plot I want and engineer them. You can’t just bend them to your will. And if the character won’t bend, you have to let them do what they want and see what happens or you have to come up with a different endpoint that they can be nudged into. You can’t nudge them with another character acting out of character. You can use characters acting like themselves, plausible natural events, and OCs.
It's a character who is fully developed to the point where they feel as "real" as a fictional character can be. Complicated, deep, dynamic, surprising, growing, changing, learning... Where they came from, who shaped them, what they've experienced so far, how they view the world and their place in it, goals, dreams, hopes, fears... The more angles and dimensions an author gives them, the more real they will seem. And all those aspects need to work together as organically and logically as possible or the character will break apart into a hundred separate characters wearing the same face and name.
To do this well, the author must be subtle and clever in how they show/reveal/develop the character's history and personality through interactions with other people, inner monologues, actions, reactions, dialogue. The writer can't just infodump a list of character traits and then expect the reader to 1) remember them all and 2) accept them without any proof within the story. You don't have to state that a character is smart - show them being smart in diffferent situations.
For me it's basically how well they fit into the story, how well they play their role in that story, and whether they're portrayed in a believable and relatable way. Honestly, though, all my criteria are extremely subjective. I consider a character to be well-written if I like them a lot, even though from an objective standpoint they might not actually be well-written.
I think it’s about whether the character is believable. Can you view this character as a real, living person? Are their flaws realistic and do they impact their decisions/actions in a believable way? Are their strengths reasonable? Do they interact with other characters that make sense given their relationship, experience, history, etc.
These are a few traits I love to look for: 1. **Depth:** A well-written character has depth beyond surface-level traits. They have a backstory, motivations, desires, fears, strengths, weaknesses, and contradictions that make them feel like real people. They should be capable of growth and change/learn throughout the story. 2. **Be consistent:** While characters should be complex, their actions, thoughts, and behaviors should be consistent with their already *established* traits, values, and experiences. 3. **Have their own thoughts:** These characters don't always just react or nod to events happening. There are moments where they too take charge and give their own opinions on what they think should happen. It could be a wrong choice, but it's still one they made. We don't have to agree with it, but if they have a reason to do it, it's great. 1. E.g., I don't support mass genocides for a cause, but I also understand why Thanos is written the way he is. He isn't fundamentally cruel; he just doesn't want Titan to repeat. 4. **Moral dilemmas:** Characters with internal conflicts, such as moral dilemmas, emotional struggles, or conflicting desires, are far more compelling and relatable, than a character who's just overly awesome at everything. 5. **External dilemmas:** Characters should also face external challenges and obstacles that test their abilities, beliefs, and resolve. Now, they don't have to go to space and sacrifice their life to stop an alien invasion. 1. Even something as simple "I'll stick to my guns even if it's an unpopular opinion" will do. 6. **Voice:** Let's not have cookie-cutter characters. Each character in a plot should have their own distinct personality shining through. 1. Think of your favorite Power Rangers show, and think of how each character is portrayed. They all wear the same suit, but their personality is what distinguishes them apart. 7. **Growth/Arcs:** Characters should develop and change over the course of the story, whether it's through overcoming obstacles, learning from mistakes, or challenging their beliefs. This is kind of an optional thing for me, since characters can be the same jerks they were, but if I were to read a fic where someone went through a life-altering event, I'd for sure expect them to not be the same as they were before. 8. **Realism/Relatability:** By this, I don't really mean, "well I wouldn't make the same choice if I were them, so they're not relatable/realistic at all". Everyone is different. Characters who evoke empathy and connection from the audience are relatable to me. I may not understand their choices/journey, but if it's important to them, then so be it. I won't relate to the experiences, but I *can* relate to the feelings of frustration, hard work, etc., should I be going on a journey that's important to me. Well-written characters are just...human. Good or evil, jerk or not, just don't make them cardboard characters with no sense of personality.
>Growth/Arcs This is a big one for main characters, yes. A side character in three chapters may not have access to enough of the story to do this, but someone you follow for 50k, 100k, whatever words you would expect it.
Personal opinions of course: At the most fundamental level, a well written character is one who engages the audience and creates emotional responses in the way the author intended. Everything else is a secondary addition to help guide the kind of character you're trying to make. Now, for most characters what people mean when they say they're well written, it usually means they're believable, full fleshed out people who don't simply appear to be custom made for the story. This is where I believe your Paul Atreides comes in. Paul Atreides is set up to be this prophet, this ubermensch, the culmination of generations of Bene Gesserit breeding programs and lies. If he went in going "Hell, yeah, that's awesome. Let's fool these rubes, bang some hot desert chicks, kick ass and take names." Then he wouldn't be quite as well written to most people, despite that being a perfectly reasonable response. Repulsive, but if you're telling me you haven't met someone like that, then I'd say you've had a blessed life. But Paul has layers. He is conflicted by the Bene Gesserit lies. He loves the fremen and Chani, he doesn't want to abuse their trust. But he also wants to destroy the Harkonnen's get vengeance for his murdered father, and take his place as duke. And he is drawn to that power of prophecy that he also fears. In this way, it is three things that make him feel so well written. The first is obvious, all these impulses I've described make sense. The viewer can watch that and nod along going, it is reasonable that they would feel those ways. The second is more interesting, these feelings are in conflict. It is not enough to have all these layers, if they all point them toward the same direction. He is torn between his love and responsibilities, his desires and duties, his relationships and the culture he has become part of. To quote Faulkner: The only thing worth writing about is the human heart in conflict with itself. And lastly, the narrative itself is built upon those conflicts. Paul may have all those character traits that I've listed above and more. But if I take Paul, pluck him from Dune and dump him in, I dunno, a palace romcom staring him and Irulan, set after the events of the movie. Then I could change literally nothing about him, and he wouldn't be as well written a character, because the the comedy of him having a meet cute with Irulan has absolutely nothing to do with all that juicy conflict. So that's one. But, there is another. There are some characters that are somewhat often scoffed at as being lesser than that first kind, that I fundamentally disagree with. There are characters who do not have many layers, or maybe none at all. They are not always consistent in their characterization. There's little to no internal conflict bubbling up inside them. But what they are, is fun to read about and interesting to engage with. These are your Paddington Bear, Superman, the Joker, Darth Vader in ANH and the Emperor in RotJ after Vader got layers added to him, the Wicked Witch of the West, Captain America, most the Knights of the Round Table. They're your snarky sitcom characters who you just have to sit and watch every week. These characters tend to have a deep defining characteristic and then are put into situations where that gets revealed over and over again, in interesting ways. And the only way to really pull them off is to be engaging, in whatever way the writer can make work. The jokes got to continuously be on point, the horror has to be consistently disturbing, the nobility must be tested and preserved.
whenever you have a value judgement as "well" or "good" it's gonna be hard to define because it's inherently subjective I think it's easy to get tempted to define it as "realistic", but I don't think that's really the whole truth. Sometimes realism doesn't feel realistic in fiction. There are people in real life that are very flat and boring or that have motivations that are impossible to understand. And sometimes there are interesting characters in fiction that can't really have a real life equivalent when people say well written they probably just mean compelling. A character that you get invested in. And that's usually because they have depth and complexity, understandable motivations, they have established history and relationships, and all those things connect with each other in some way. So I guess you could also call it the character being *thoroughly* written, or there has been a lot of effort put in characterization. but also, some characters do not need to be and should not be complex in order to fill the purpose they serve within a story. I would still consider those characters to be well written, because they are exactly as complex as they need to be. So... yeah. I don't know.
I live and die by the Rule of Three. If you can name three *different* aspects of a character's personality (not appearance, not profession, not role, not relationships) then they have enough depth to be worth being the focus. One-note characters are boring or comic relief. Two-notes make good supporting characters, foils, or enemies. People you want the reader to recognize by their words and actions. But if you're going to follow the character for a while, you need more than "he's a patriot and he's compassionate". I agree with u/waiting-for-the-rain and u/SpartiateDienekes about consistency and layers, especially when paired. A character *cannot* be consistent, if we know nothing about them, their thoughts, their feelings, their wants and needs. Yes, a character could always have an easily-bruised ego or a soft spot for children, but if that never shows up until Chapter 57, it's going to *feel* out of nowhere. The more layers a character has, the more they *can* do that will feel like something they *would* do. u/chshcat mentioned characters being complex, I think we're talking about the same thing. It is also much easier to write a struggle a character has, when there are competing features that character has. A character is a patriot, but has a soft spot for children. Okay, cool. He finds a couple of starving orphans, in his own country, whose other-country parents just died in the war. Now what does he do? Take away either aspect, and there's no conflict. Now, there is. If nothing else, you can start "putting the layers in order" by having the character show which motivations are more important to them, which personality features are more prominent. What finally gets that strong, silent, stoic character to start screaming in rage? To break down and cry? To smile or laugh? If you cannot find enough aspects of a character to invent a situation (even if it's not in your work) that would create a conflict between those aspects, *there aren't enough aspects*. Relatable is important, compelling is important, boring is *unforgivable*. Hopefully you got what you needed out of the well-written posts here and possibly also mine.
Personal opinion, bear in mind that all of these are guidelines not rules and can be broken individually: 1. A well-written character has **something they want**, and they want it badly enough to keep the plot moving. It is *possible* to write a narrative about a passive protagonist who primarily has things happen *TO* him (see: Rincewind from Discworld) and have that plot be clever and fun to read, but it's a challenge. 2. They have **strong beliefs about the world** they live in. Think: Arthur Morgan from Red Dead Redemption, and his feelings about the encroachment of industrialized civilization and the death of an era. Think: Aziraphale and Crowley from Good Omens, and their deeply-held and deeply-conflicted feelings about the roles of Heaven and Hell. These can be moral or political stances, but they don't have to be. They also don't necessarily have to be *right.* A compelling villain should have their own beliefs and justifications! 3. Those beliefs should, at some point in the story, **come into conflict**. Either with the situation, or (even better) with *each other!* We love a deeply-written character who has to struggle to balance their priorities, or reckon with the consequences of their actions. To continue the above example -- Arthur having to come to terms with the reality of the consequences of his wild, free-living "outlaw code" and the way it tends to end in brutal violence done to the people he loves. 4. They should have **enough little details to add depth**. Think about it like a drawing; you can have a really well-proportioned figure sketch, but what makes it come to life is the shading and the detail work. This isn't a substitute for the above three things! For me, a common mark of a beginner writer is that they throw a bunch of quirks (e.g. favorite food, catchphrase, etc.) on top of a mostly-flat character, when it should be the other way around: get your bones right first, then flesh them out. EDIT TO ADD: this is again a personal opinion, but I try not to think about my characters in terms of strengths and flaws. Any strength can be a flaw, and any flaw can be a strength. A character whose strength is their loyalty, can be swayed by that loyalty to turn a blind eye to awful things done by their loved ones. A cowardly and weak-willed character can be the only one smart enough to run away from an overwhelming threat, and they get the warning out while the heroes with bravado are slaughtered. It's more important to be willing to commit, so that trait both helps *and* hinders them -- a mastermind who meticulously plans every detail should be thrown off and stumble when that plan goes off the rails, not magically turn into an improviser who can perfectly play it by ear.
To me, a well-written character consistently acts based on their internal logic. Even if you don't agree with their motivations (for better or worse), you can understand what makes them tick. They have their own reasoning and their behaviour stems from it naturally.
Don't carry for this being the main style when I read an watch stuff I do love playing around that noggin of there's when they interact with anyone K: series is full of it lol
It's not one thing. It's many that work together. The character and the story work together. They both make you feel. The character has more to them than what the plot demands of them. Sometimes well-written means that there are many things that they say that are so undeniably them
They feel real. Like a Person. You feel like you would know them in real life and that they have a distinct personality with flaws, quirks, interests and hobbies.
For me it's a character that spund like they could be human. Or when they act like real people.
As someone whose fandom had a lot of writers room turnover, has no show bible establishing how various characters are supposed to go, and who has no continuity editor: its not how they act. The late seasons of my show are running on pure charisma. The actors have it in spades. They’re constantly being given wtf self-contradictory lines, temporary amnesia, sudden and bizarre changes in personality, and somehow they keep you sucked in. The writing was amazing s1-2 and after that its just gets lost and the actors are carrying everything. I think a well written character needs a consistent personality and motivation. If the world affects them, it can change their motivation (e.g. something matters more to them now, or something happened to traumatize the) but it shouldn’t drastically change their personality. What happens in the changed situation should be something they would do with their same personality. I think the problem the writers in my show had was that they inherited a show they didn’t want and they wanted to force it to be a different show. They had long term result ideas and they tried to bend the characters to fit their result, not write what the characters would have done in the situation. To do this they rely on all kinds of weird things. They decided they wanted a will-they-won’t-they, so they made character B forget that character A is shit for communication and just sit around passively (writers forgot B is assertive and would just have a conversation) waiting for A to figure out their feelings and tell B using the exact words B wants and not synonyms. They make B legit forget when A actually did say they loved B. They made A break up with C to be with A, then start beating themselves up over having not broken up with C which literally just happened. They had goodie two shoes B try to kill A for reasons no one understands, because they thought it bought them entry into their season plot idea. There’s so much fake drama and ridiculous soft reboot premises each later season its ridiculous, hence the many rich opportunities for fixits and whatifs. There are a ton of stories that grow out of the many, many cases in which a reasonable fan might ask: what would happen to this part of the story if all the characters behaved as established before the guy who wrote the pilot stopped consulting? Because that’s when characterization started going to Hell. I think if you have an overarching plot idea and you want to write a good character, you have to listen to them. You either need to sit around like an engineer and figure out what specific things can nudge this character into the plot I want and engineer them. You can’t just bend them to your will. And if the character won’t bend, you have to let them do what they want and see what happens or you have to come up with a different endpoint that they can be nudged into. You can’t nudge them with another character acting out of character. You can use characters acting like themselves, plausible natural events, and OCs.
It's a character who is fully developed to the point where they feel as "real" as a fictional character can be. Complicated, deep, dynamic, surprising, growing, changing, learning... Where they came from, who shaped them, what they've experienced so far, how they view the world and their place in it, goals, dreams, hopes, fears... The more angles and dimensions an author gives them, the more real they will seem. And all those aspects need to work together as organically and logically as possible or the character will break apart into a hundred separate characters wearing the same face and name. To do this well, the author must be subtle and clever in how they show/reveal/develop the character's history and personality through interactions with other people, inner monologues, actions, reactions, dialogue. The writer can't just infodump a list of character traits and then expect the reader to 1) remember them all and 2) accept them without any proof within the story. You don't have to state that a character is smart - show them being smart in diffferent situations.
For me it's basically how well they fit into the story, how well they play their role in that story, and whether they're portrayed in a believable and relatable way. Honestly, though, all my criteria are extremely subjective. I consider a character to be well-written if I like them a lot, even though from an objective standpoint they might not actually be well-written.