Hisoka Hunter X Hunter Hisoka is such a creepy yet powerful guy. He's a huge Gon fanboy and gets an erection just from the thought of Gon getting stronger and more powerful. He's definitely my favorite anime Villian of all time.
HONORABLE MENTIONS Asura Soul Eater
Esdeath Akame Ga Kill
"Tobi" Naruto Shippuden
Satsuki Kill La Kill