The thing about knowing how the human mind is put together is that you begin to spot when a character isn't "complex" but rather has a logically impossible personality. Something that can only be resolved by multiple personalities disorder, if at all.
Take Xander Harris in BTVS. He's a white knight and a genuine hero. That makes him a Gaian of reasonably high Presence. Logically, he should have the lower Presence levels of Gaian. In particular, he should be a grey man who fits in with any situation without ever standing out, like Clark Kent. And he should be a survivor willing to cut the throat of anyone, anyone at all, in order to LIVE!
Instead, he's the exact OPPOSITE of a grey man and a survivor. But that at least can be explained by him being a blatant fucking hypocrite. A person who has ideals and principles and imposes those ideals and principles on OTHERS but NEVER ON HIMSELF. Yes, that works as an explanation, the scum sucking son of a bitch!
But no such explanation is possible for Willow who in the very first episode is a hacker (psychopath!). She goes on to becoming a traitor (psychopath) and is ever amoral (psychopath) and reckless (psychopath). And she's quite the eager little cultist (psychopath). And that's WITHOUT looking at what she does hopped up on "dark magic". She's not schizoid either but a straight out psychopath.
Problem is, she's also loyal overall (not a sociopath of any kind) and she is very, very much obedient to authority figures (right-wing authoritarian or moralist) and an eager little drone (moralist) and yes man (moralist) and adjutant / teacher's assistant (right-wing authoritarian). And there is ABSOLUTELY NOTHING that can make those personality types fit together.
In fact, those personality types can't fit together IN THE SAME ROOM. The moment you have knives available anywhere in that room, one of them will try to stab the other. And if there aren't any knives, they'll make a shiv. The weaker (mentally) the characters, the longer it will take for their minds to turn to thoughts of killing the other. But it will happen, inevitably.
You might as well ask Batman (right-wing authoritarian) to get along with the freaking Joker (psychopath). Oh except you wouldn't because the idea is totally fucking ridiculous! Similarly, put them in the same room ... as kids with undeveloped personalities, and you'd still expect sparks to fly.
So when an author writes 'shy little Willow' as a gutless backstabbing psychopath uncaring of anyone's feelings who wants to enslave, mind control and humiliate her "best friend" Buffy Summers, they're not exactly breathing fresh air into the character. They're just writing her far more consistently than the psychopath Joss Whedon ever managed to. And picking her dominant personality to boot.
And giving that egotistical selfish heartless narcissistic little bitch Buffy Summers exactly what she deserves. Because if there were any justice in the world then psychopaths would all be killed and narcissists would all be sold as sex slaves. It's not just what the Good people of the world want ... it's what the Evil people want too!
And not just because Evil people hate other Evil people, although they do. They really, really do. But because psychopaths don't care about consequences even to themselves, so they DON'T CARE if they go to prison or end up dead for doing something. They CAN'T CARE because not caring about consequences is WHAT MAKES THEM PSYCHOPATHS. And what makes them dangerous too.
Meanwhile, narcissists actually WANT to be sex slaves. They FANTASIZE about it. Who the fuck do you think writes all those semi-exhibitionistic pro-humiliation self-abasing sex slave stories? That's right, their authors are narcissists. And they are so not because they necessarily want to be the center of the universe, but because they firmly believe that *A* person ought to be the center of the universe.
Meanwhile, right-wing authoritarians are perfectly fine with homo sapiens getting slaughtered like cattle or other homo sapiens being sold as slaves, sexual or otherwise. It's a time honoured tradition!! 99% of human societies throughout 99% of human history had slavery and genocide. Even to this day, we STILL have slavery and genocide out in black Africa. What could possibly be wrong with something so NORMAL!?
Note that right-wing authoritarians are perfectly fine with killing each other so long as it's done across ethnic or national lines. Really, killing Evil people isn't a problem for ANY Evil person. Though preferably, it's other Evil people that are going to die if they get their way. Evil people will put their lives on the line to kill other Evil people.
The only people who want Evil people to be treated like human beings (and psychopaths AREN'T human beings, they're mindless animals who've accidentally mastered the trick of human speech, and I can prove this!) is Neutrals. Because being neither Evil nor categorical mortal enemies of Evil (render Evil unto Evil!), they don't have an instinctive grasp of what Evil *IS*.
Finally, when you've shown that the world could be improved by targeted mass killings and enslavement, this constitutes powerful evidence that the world is as fucked up as it can possibly get. Something I've known to be true for a long time now.