The Maestro from Peter David’s Future Imperfect. Big, evil Bastard…and he’s the Hulk too!
James Stenbeck from As The World Turns.
Mimi Bobeck from The Drew Carey Show
Kate from East of Eden
Darth Vader (how is it y’all missed this great villian?)
An entire race of super-villains, The Draka from Steve Stirling’s alternate history. The descendents of Southern slavers who migrated to South Africa and hooked up with the Boers, they hate and fear all non-Draka people, to such an extent that the only way they can feel comfortable around them is to conquer and enslave them. And not in a nice way. The prospect of their conquering the world is enough to make any sane person wish for a nuclear Armageddon.
Also, the quietly psychopathic girl from a little-known horror novel, “Let’s Go Play At the Adams’.” She’s a one-person argument for abortion-on-demand. Actually, she’s a one-person argument for abortion against the mother’s wishes.
Anton Trelig, leader of the drug cartel for sponge. A drug which is immedeiately addictive, and which if you don,t take it you will be a brain dead zombie in days. He was the true ruler of worlds by addidting their leaders, and then getting those same leaders to addict other rulers.
He later gets his hands on a super computer which can alter reality.
Nice list Bearflag70, but you forgot a couple who make all the others look like wimps:
Baron Silas Greenback, the world’s most evil toad and
Simon Bar Sinister, for my money the worst of the evil scientists around.
If you don’t say Billy Mumy from the “It’s a Good Life” Twilight Zone episode, he’s gonna send you to the cornfield.
Barney. No question about it (not the first one, but the second two? Oh yes…)
Dr. Mabuse from the German novels and film series. A classic criminal mastermind/mad scientist who uses elaborate schemes with hidden motives, underlings who never know who they are actually working for, mind control, murder, and disguises to control his criminal empire. Even though he is rarely seen, his prescence is felt because he could be anywhere. Anyone could be working for him (whether they know it or not), or even be him in disguise.
Stormbringer, the souldraining living sword from the Elric novels. How do you strangle a living sword by the way? Very carefully?
The head of the clan after Ogami Itto in the *Lone Wolf And Cub * films. He’s willing to sacrifice his family and thousands of servants and warriors to kill one man and his son.
hello?
no one mentions the epitome of bad guy?
Snidley Whiplash!
Greatest villain is definitely Joseph Heric, from The Practice. The way he manipulated the law to get away with three murders is nothing short of masterful.
Cigarette Smoking Man
Alexis Carrington.
And of course my obscure, only-recognized-on-the-internet-vote:
Shockwave from Transformers. (Megatron who?)
Damn you, Atreyu! You took my vote! Gonna have to steal your gold and frame your kinsman for it.
Ok, well how about Burke, from Aliens?
Nah, he’s the kinda guy you’d just squish. I thought Spacey in “Seven” was just ridiculous. Now, for a serial killer you don’t want to mess with, I’d have to vote for the Hannibal Lector in Manhunter.
But for the really bad guys, you gotta go with the classics.
Like, how about Richard III? Yeah, he’s real nasty.
Ooh, ooh! I know! Tartuffe especially as played by Sir Antony Sher who also played Richard III.
Now here’s a guy who, pretending to be a pious, self-flagellating monk, worms his way into a man’s household and trust, steals his money, corrupts his children, and nearly seduces his wife. you watch him, and you just wanna shoot him dead.
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Professor Moriarty (sp? sorry) from the Sherlock Holmes stories. The original criminal mastermind- and more than a match for Holmes himself.
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Vader in the first two Star Wars movies- till they wussified him in Luke’s great Ewok adventure-- oops, I mean Return of the Jedi. Mmmm force choking annoying people on video conference calls with your boss- oh yah Vader I’ve been there. “I am distrubed by your lack of faith”-- excellent.
-me
You’re talking to the SDMB’s resident Transformers junkie here. 
Anyway, in a related vein, I’ll toss in a vote for Megatron from the Transformers-spin-off Beast Wars cartoon show. Not only does he weave plots within plots, not only does he carelessly kill his own troops when they are no longer useful, not only does he want the heroes dead and gone, but he’s willing to alter reality itself to do all of that. Even Lex Luthor never tried to go to Krypton and annihilate the infant Kal-El (barring several goofy imaginary stories, but those don’t count).
“The future has changed! The Autobots LOSE! Evil TRIUMPHS! And you … YOU - NO - LONGER - EXIST!” (The Agenda, part 3)
And a sympathy vote to Emperor Zurg from Toy Story 2. How can you resist a baddie with a “Zurg vision” peephole?
Hey! Hey! HEY!
I also have good taste in jewelry, and I’m strongly goal-oriented.
Hmm. I would say Magneto , but he’s got a reason for being a badguy.
So, I have to place my vote for The Kingpin of Crime as the baddest of the bad. (C’mon. He’s like a Lex Luthor who can actually fight. You know you agree. :D)
Marvel’s Carnage. He killed for the sake of killing.
Henry Bendix from Stormwatch. “I’ve got your New World Order right here.”
Shere Khan from the Jungle Book. I loved the guy who did his voice.
I’d have to say The Joker, but only when he’s done right, aka The Killing Joke. Sometimes he’s done as just too silly - but not this one.
The most evil character I ever saw was when Ren, from Ren & Stimpy, swallowed a magic potion that split him into Evil Ren and Apathy Ren.
Evil Ren was so evil that he drank the potion again and split into Evil Ren and Heinous Ren.
Heinous Ren was so evil he drank the potion again and split into Heinous Ren, and the most evil Ren of all, FEMALE REN!
AHHHHHhhhh, I shudder as I type this!
-Sandwriter