Scorpius from Farscape
The Monarch is the butterfly-themed archnemisis of Dr. Thaddeus Venture on The Venture Brothers. If you haven’t seen it, you need to.
The Monarch’s girlfriend is the treacherous and deep-voiced Dr. Girlfriend.
Almost forgot to post my favorite Monarch quote:
“I’m not even going to flush! Let them see the wrath of the Monarch!”
Anubis from Satrgate.
Col. Samuel Flagg was inMASH
Randall Flagg, AKA the walkin’ dude, was in The Stand - which was a miniseries.
Swith the first a and the first t in the third word of that last post
The Mayor from Buffy Season 3
Sideshow Bob from the Simpsons esp the one when he and Bart team up to stop Sidesow Bob’s brother (Voiced by David Hyde Pierce)
Arnold Rimmer from Red Dwarf
The Master, from Doctor Who. (Especially in his incarnation as Roger Delgado … the very quintessence of villainy.)
From more serious BBC dramas: Kessler, from Secret Army. And Patrick Stewart as Sejanus in I, Claudius.
As evil as Sejanus was, Livia had him beat by a mile on the evilometer.
Servalan from Blake’s Seven
From The Shield: Armadillo Quintero (Season 2) and Antwon Mitchell (Season 4).
From Justice League Unlimited: Amanda Waller.
more from “Buffy”:
Spike(much more interesting as bad guy than as a neutered, pining for that stick figure Buffy)
Faith (again, much better as a bad girl than as a reformed bad girl)
Drusilla
from “Angel”:
Jasmine
evil Cordelia
Lindsay
from “Cheers”:
Gary of “Gary’s Old Towne Tavern”
from “Batman”:
Catwoman (Julie Newmar)
from “WKRP in Cincinnati”:
the pig mascot from the rival rock station
And let us certainly not forget **the Legion of Doom! **
All these Buffistas and no one has mentioned Angelus? Not to take anything away from the Mayor, Spike, or Dru, but no one fucked with Buffy’s head like Evil Angel in Season 2. The drama! The angst! The super creepy seduction of Drusilla! And, unlike almost every other Big Bad, he actually killed someone we liked.
Oh, that’s right! Angelus was downright evil.
I nominate the entire Klingon race from Star Trek: TOS. Those guys were mean.
#2 - The Prisoner
The Iron Sheik - WWF
Dick Dastardly - Wacky Races
Boris S. Swartz - J.P. Patches
Boss Hogg - The Dukes of Hazard
Lt. Chapman - Rockford Files
mungo…no one else knows what we are talking about,
but it was Boris S Wort (the second meanest man in the world)
Dan fielding a villian? Dan’s not a villian, he is my hero!
He almost got more tail that any three other characters I can think of. 
Kirk clearly got more tail, and Alien Princess Tail, too.
So, getting c*ck-blocked a record number of times makes him a hero to you? What kind of hero, a role model of some sort?
Sorry to hear it. 
Anyway:
Mojo Jojo – The Powerpuff Girls
Mandark – Dexter’s Laboratory
Vicky, Mr. Crocker – The Fairly Oddparents
The Bronze Kneecap – The Adventures of the Crimson Chin
Aku – Samurai Jack (see? I can so come up with a really villainous villain)
Zorak – The Brak Show
Dishonest John - Cecil & Beanie (nya ah ah!)
Alexis Carrington- Dynasty
Ava- Nip Tuck
Zach- Desperate Housewives
Mr. Drysdale - Beverly Hillbillys