Easily, to me, the answer is
Malificent.
Now, I think there are a lot of people in this thread that are siding with a few of the villains simply because they killed someone, but if you remember correctly Malificent's spell was intentioned and cast to kill Aurora before her 16th birthday, I mean, as a child! It was only because the fairies were able to
weaken her spell that Aurora is destined to live.
Malificent's name alone means
Evil-Doer. She appears in the castle for the christening via a shot of green lightning, people! She kidnaps Prince Philip and taunts him saying she's going to keep him for 100 years and then release him to wake the beautiful and ageless Aurora while he is crippled and nearly dead. She casts lightning, creates the forest of thorns and turns into a dragon the size of a castle to summon "All the powers of Hell!". As she falls to her death she still lashes out to take Philip with her.
Additionally, if you take into consideration this was released in 1959 and play that against the 90s and 00s the movie makers can get away with a lot more evil doing. Should this be re-made right now? She would literally
own the souls of all living beings. I'm just saying.
She is to her dying breath the very embodiment of menacing, evil
power, and even in the extended Disney universe she continues to be a recurring villain that often leads the others in the charge against good. She'll always be my favorite at heart. :)
(And to top it off she wears "Horns of the Devil"; I mean seriously- how can you compete with that?)
