I say that would have to be Jakotsu of the Band of Seven. He's a male homosexual homicidal maniac that just loves to chop up the cute boys--maybe I can relate dunno... more like cute girls for me, choppy choppy >xD Really imagining this is making me feel giddy, maybe I should stop ... o\,..,/o

Naraku. Soooooo very Definitely Naraku. This guy is nuts seriously!!! Jakotsu is pretty crazy too which makes sense. Both he and Naraku are Yandere. Whole thing explained right there.
Naraku is all like "I'm completely obsessed with you. I have fantasies about making you cry. I want to kill you. Let me kill you!"