It sounds crazy, and I'm sure a LOT of you probably haven't heard of this one, but let's see:
Yep, Percival C. McLeach, who in my own opinion, dominates the ultimate villain list in Walt Disney history, and it really opened my eyes because in SOME aspects, Disney managed to make him likeable, and it helped me to understand that villains just don't need to be super-evil and wreck havoc all the time. They laugh, they cry, they have feelings, and a LOT of issues. They're still human.
When I saw "The Rescuers Down Under" I was shocked at what this villain did - and in all my years, I have yet to see a villain that's worse.
This dip-stick kidnapped a young boy, chained him in a shack, performed sadomasochistic acts on him, tortured him, let wild animals loose on him, and when the boy managed to escape, the villain hunted him down in the Australian Outback and tried to shoot him dead - all just so he could kill the last golden eagle on Earth.
Now THAT is a villain.