Manson fav, but Hitler was best, he mind controled an entire nation into killing machines. I don't agree with his views or ways, but if you had to pick a best, it had to be him. He was like cancer if you rated killers by dieses but genius part about it is he never layed a hand on his victims.
I chose Hitler simply because I am fascinated that someone could be that warped. The man was a genius, but seriously deluded.
