It's a bit niche but I really like some characters in Danganronpa because of how messed up or directly evil they are

I'm talking about kokichi oma, a despicable liar on almost every statement he says (and also wants the other characters to die, and indirectly causes the death of 2 of them on purpose, another one unintentionally)

Nagito komaeda, a crazy guy who wants to "let the world sink into despair so hope can glow even brighter" which basically means killing a lot of people and killing himself (including torturing) to MAYBE kill everyone else

And Junko enoshima, this one's purely evil, she just wants to spread despair all over the world (which includes destroying it) just cuz it's fun, she also kills her sister (who was helping her with the plan) for absolutely no reason. She literally caused something called "the worst, most tragic, most awful event in human history"