I thought that I had already posted in here, but I guess that I hadn't.
I have two favorite villains: *SPOILERS*
Freeza: Freeza's just a rutheless tyrant that enjoys toying with our heroes, as well as their lives.
King Piccolo: King Piccolo is just awesome. Not only is he one of the only villains to get his wish granted, he destroys the dragon after making his wish! Another thing that is great about Piccolo is that he accomplishes his goal of taking over the world (although his dominion was short lived). To add to all of that, he was planning to destroy the world by drawing lots each year. Piccolo is a great villain.