I think it really depends on what the character is meant to symbolize and why?
There are some pretty interesting assassins out there (Kill Bill for instance) and there are sociopaths and things like that. (side note: I bring up Quentin Tarantino’s movie because most of his films are really consciously about the idea of revenge and its relationship to culture)
Honestly I feel like our culture is way too obsessed with sociopaths and serial killers, maybe because of how shocking and alien they are but maybe because if you can label someone a sociopath then they stop being fully human (they don’t feel empathy so why should we?)
I’d like to believe that we can enact fair punishment which if needed, separates them from society so that they cannot harm anyone. At the same time it doesn’t preclude the concept that at sometime in the future, (maybe the distance future) that that person who did something horrible is going to realize what they did was wrong genuinely feel remorse and repent.
I’d like to believe that everyone is capable of changing even if right now they deliberately choose not to.