Bily Rotner and the Captain Underpants villains

The Lord Protecter from The Beast of Buckingham Palace.

Voldemort from Harry Potter

Euron Greyjoy (A Song of Ice and Fire)

Morgoth from the Middle Earth saga.

Sebastian Morgenstern, pure evil done right

Luke Castellan, the classic mistake of trying to fix the future by bringing back the past

Annie Wilkes, frighteningly realistic

W.I.C.K.E.D., see above

@TTerrin some of those aren't even from books or villains