1. Jafar & Iago - Maybe just because Aladdin is my favourite Disney film, but Jafar rocks. The scene when he gets hold of the lamp and does that evil crazy laugh after shooting Aladdin off into the sky in that building is seriously demented and scary.
2. Scar - Possibly the most evil villian. Can't really top murdering your brother, then trying to murder your nephew. I think deep down he knew he was adopted or something because he looks nothing like the rest of the family.
3. Cruella De Ville - I'm still scared of her, which speaks for itself really.
Other good'uns are Maleficent (very scary), Captain Hook (very camp), Rattigan (very psychotic), Medusa (very creepy) and Hades (very funny).
It's not suprising that most of us are still scared of creeped out by these characters as Disney films were probably our first sense of good and evil and the villians had a lasting effect on us.