I just amor how he has so many of the qualities a classical villain needs to have without being completely overbearing. He's also totally un-corruptible in the sense that there's essentially no hope for him to find his way over to the "good" side. He manages to creep me out and make me fangirl at the same time, and he's not a complete and total moron like many villains tend to be. He really lives up to his título as being a paranoid sociopath.
Well, Suigintou is the first doll of the Rozen Maiden collection and is the one with the strongest amor for the Rozen Maiden's father, Rozen. However, Suigintou was never finished, making her envy the other Rozen Maidens. When she first took place in the Alice Game, Suigintou was naïve and didn't truly understand the purpose of the other Rozen Maidens fighting each other to the death. She was taken down por the one sister of hers that she trusted, Shinku. Feeling betrayed, Suigintou turned bitter, now a cold and cruel Rozen Maiden, who vowed to win the Alice Game no matter the price.
[Technically, she's my segundo favorito! villain. First is Miyo Takano from Higurashi No Naku Koro Ni but since I don't usually post Suigintou, I thought I should give her some amor as well. :)]