andrea cavalcanti ( gankutsuou ) bastard is truely insane and sick ..slept with his birth mother ( she didn't know he was her son) and try to marry his sister. all as revenge for them abandoning ( and more) him as a baby ..he also killed alot of people...but he's so entertaining to watch!
Arlong. This guy is the epitome of psycho. Not only does he have a massive, toothed sword, but his teeth can break pillars and buildings, just from a bite. If that wasn't enough, he's super-strong and believes that humans are inferior and so he kills them at ease, because he feels like doing so. Also, he made Nami-chan cry. Bastard! Just look at him.