Famous/Infamous Villains

In addition to to those already mentioned

Schillinger from Oz

Megatron

Denzel in Training Day

Bane in the Batman Knightfall saga

Joker (both Heath Ledger and Mark Hamill)

Does Gaius Baltar from battlestar galactica count? Or is he more of an anti hero?
Oohhhhh good question with Gaius
Kind of like John Locke or Ben Linus on Lost it depends on which part of the story
When he was hiding evidence and manipulating data about cylons definitely a villain
He was probably the worst when he was the puppethead on the colony
But he was ultimately redeemed, no?