Sidious, of course. He manipulated an entire galaxy. Shows how smart some people are. After seeing the PT I don't consider Vader as a villain, but a victim. Dooku just should have never existed as well as Grievass. Maul was good but since he was in half of one movie I'd just consider him to be a henchman. And Jabba was just a side plot, he really didn't do much in the purpose of villainy, just a mob boss.