One of HBO's many popular television shows, "Deadwood" features the rough-and-tough Al Swearengen. This dude is so bad-ass, he sent a group of his henchmen out to kill an entire family on their way back from Minnesota, ordered the death of a land owner who wanted reimbursement for useless land sold to him by Swearengen, and repeatedly tossed dead bodies to Mr. Woo's pigs.
JR Ewing, "Dallas"
One of the most popular characters in one of the late 70s/early 80s most popular shows, J.R Ewing was a devious villain. Not only was J.R a major playboy who cheated on his wife, but he would do anything to get what he wanted, including hurting his own family members and involving himself with corrupt members of law enforcement. In fact, he was so hated someone shot him during the 1980 season.
What started out to be a very promising NBC television series, "Heroes" quickly turned into a clunker after the first season. However, the T.V drama did have one saving grace: the character Sylar, played by Zachary Quinto. Sylar had developed the ability to take other peoples' powers and make them his own. After taking his victim's powers, he often murdered them. He also managed to bang a hot looking Mexican chick after killing her brother.
The Wicked Witch of the West, "The Wizard of Oz"
Probably even more so than J.R Ewing, The Wicked Witch of the West from "The Wizard of Oz" is one of the most well known villains of all-time. Not only is she extremely hideous, but the crazy bat has a horde of ugly flying monkeys, which she ordered to capture Dorothy so she could destroy her…and her little dog, too! The Wicked Witch of the West is ranked by many as the number one female villain of all-time.
Katherine Pierce, "The Vampire Diaries"
Not only is Katherine a sexy, manipulative, selfish villain; she also happens to be a vampire. Since vampires typically live a long time, she has been tormenting, conniving and murdering for years. The popular "Vampire Diaries" villain will do anything to get what she wants, even if it includes killing her own kind. She wouldn't exactly fit in with the goody-goody Cullens on "Twilight".
Dr. Doofenshmirtz, "Phineas & Ferb"
This list would not be complete without a cartoon villain. While there are many to choose from, Dr. Doofenshmirtz makes the list because of his crazy "inators" and his epic battles with nemesis, Perry the Platypus. Additionally, his brother happens to be the city's mayor, and the residents adore him. Many of Doofenshmirtz's inventions are geared toward making his brother look bad so he can take over the city. The wacky villain also has a rebellious daughter and an ex-wife who unknowingly finances his crazy contraptions through her alimony checks.
Number 6, "Battlestar Galactica"
It's difficult to choose among the cylons in "Battlestar Galactica as the main villain, but Number 6 killed a baby, seduced a scientist into revealing a defense code that lead to the destruction of a planet, and detonated a nuclear bomb aboard the largest civilian ship in the fleet. To top things off, like most popular female villains, Number 6 is extremely hot! And she's in Playboy!
Smoking Man, "X-files"
One of "The X-files" many villains, the Smoking Man is so popular, he is part of the lyrics to one of The Barenaked Ladies' songs. Also referred to as Cancer Man, he is a nemesis of agents Mulder and Scully because he is a main player in the government's conspiracy to cover up the existence of alien life. While he does not appear much on the show, when he does, it usually spells trouble for the two agents.