Hey man. I know what you mean, but the reason I undo it was that killing someone doesn´t make you to become an antagonist. If we have to categorize every single charater that killed someone, then we can add Carol or Daryl too. The role of the antagonist in the story is to antagonize the protagonists and they must have their motives to do so and the reason why they are killing, for example "The Governor". Lizzie is just a twisted girl, who doesn´t have motives behind it. So that´s why she is not an antagonist. And we never categorize her as an antagonist so there is the reason behind it. It also means that her Comic counterpart, Ben, is also not an antagonist.
She didn't just kill somone. She killed her own sister, her motivation being that she wanted her to come back as a walker. Mental instability does not prevent someone from being an antagonist (there would practically be no antagonists if that was the case). While Mika wasn't a main character or anything, she was allied with the main characters (Carol and Tyreese), and Lizzie posed a direct threat to them, which is why Carol killed her. Same thing with Ben, though you could argue that Ben didn't understand what he did because of his young age. LIzzie doesn't really have this excuse, and both characters exibit traits of a psychopath.
That´s true. But it can´t hide the fact that some antagonists are mentally unstable, but they still know what they doing and why they did that, for example Negan. He is a psychopath and mentally unstable in his own way, but he still completely know what he is doing, not like Lizzie, who doesn´t know what she is doing.
I mean, Lizzie did know she was killing her sister. She just equated humans to walkers (or even placed walkers above humans), and this thought it didn't matter, or that it would be better even. My understanding of an antagonist is someone who diliberately impeads on the protagonists, regardless of motivation or morality. I guess the only thing disputed here is the "diliberate" part, and I can see both sides of the argument on that one. You could argue that Lizzie isn't diliberately endangering our main characters, since she doesn't know that what she's doing is wrong, but at the same time her actions are not accidental, despite her mind being twisted. In the end, we will never really know what was in Lizzie's head, just that she was a threat to the protagonists. I guess I'm fine with either interpretation. So I'm fine with the edit, too. Good talk :)