Hero villain angst???

Idea where villain falls for hero and they like both fall in love right and hero is like "i can fix him" and theyre relationship is super cute and all but hero doesn't realize that the villain is genuinely just a shitty person with fucked up morals. So like villain kills people around the hero to eliminate "competition" and hero finds out eventually and finally realizes, 'oh shit they're FUCKED UP' and it's a whole moral debate of the world or the villain cause the villain would genuinely sacrifice the world for hero. Super cute BUT TOXIC AS HELL