In most classic novels, there are three types of villians. Nature, themselves, or another person. While some deep novels and novellas like Grapes of Wrath and Old Man and the Sea have non-human antagonists, there are some novels with good bad guys.

Othello's Iago and Richard III's Richard III are probably the two biggest villians in Shakespeare, ignoring Claudius and Edmund. Iago has those sneaky ways and incredible luck which gives him such a great bad dude. Iago has more lines than any other Shakespearean character, after Hamlet. Richard III is cool because he's that guy your English teacher told you that he was also a bad guy. In all honesty, he's a crazy dude with a broke back. And he has one of the best opening and closing lines of any Shakespearean character.

My vote for best non-human antagonists that might as well be humans are Moby Dick and Shere Khan from The Jungle Book. Both have that sinister feeling, even though they have 4 or 0 legs.

Some more honorable mentions:

Long John Silver - Treasure Island

The White Witch - Lion, Witch, and Wardrobe

The Traflamadores - Slaughterhouse-Five

Satan - The Bible, Paradise Lost, Divine Comedy

The North - Gone With the Wind

Napoleon - Animal Farm

If you have another good villian, or just want to get your name in blog post titles, post a comment.