Twisted and Dark

Sociopath and a (quite sensitive) serial killer.

Seme manipulated the ones around uke to make the latter rely on him. But he was actually someone kind of obsessive/possessive stalker?

Probably happy ending.

Not too twisted or dark, but both the protagonists are fucked up. Quite irritating to read their back and forth, but I'm in too deep to drop.

Psychopath and someone who wanted revenge for his sister