Well. Khan has already been mentioned,so I’m tossing out Gul Dukat (at least till he went kind of bonkers after Ziyal’s death.) The best villains think that they’re the hero.
The first that comes to mind is Crowley from Supernatural.
Archibald Cunningham
Dolores Umbridge - so much worse in the books than in the movies. I hate her more than Voldemort.
Robert Vaughn in Bullitt
From the comic books:
The Joker.
Lex Luthor.
Brainiac.
Eobard Thawne, aka the Reverse Flash.
From Star Trek: TNG, Q. He proved how dangerous he could be when he threw the Enterprise into the path of the Borg and they lost 17 crew members.
More recently, I like Parker Posey’s Dr. Smith.
Not a patch on Francis Urquhart
Darth Vader. Man has the best Evil Theme-song.
I nominate Destro and The Baroness, from (the animated) GI Joe, as The Best Evil Couple.
Jack Palance, in Shane.
The unemotional and inexorable Kaylons from The Orville.
Guns in their heads - cool. Flying, detachable heads with guns - cooler!
T-1000 - Built with a singular purpose and essentially unstoppable. There is no way they should have been able to escape it. Played perfectly by Robert Patrick.
Fun trivia: James Cameron originally wanted the part to be played by Billy Idol, but a motorcycle accident rendered him unable to take the role.
I view their differences as stylistic. Urquhart is flamboyant; Underwood is more subtle.
Underwood - pushes an inconvenient woman in front of a train in a dark subway tunnel.
Urquhart - throws her off the top of a building in broad daylight.
I’m not sure I agree, but that’s an interesting perspective.
I almost included Dr. Zaius from Planet of the Apes in my list. But he believes he’s doing the right thing and protecting ape society from the scourge of humans. Arguably he is doing the right thing.
I’ll second Darth Vader. Other favorites from the Star Wars universe: Director Orson Krennic & Maul.
The Kurgan from Highlander.
We all know the best villain in Star Wars is George Lucas.
Steve Martin & Rebecca Pigeon in “The Spanish Prisoner” were excellent villains.