Proof that Jack Warner is the greatest villain ever.
You’re in a movie with the guy who played Alex de Large and who later killed Captain Kirk, and you’re the villain? Greatest. Villain. Ever.
John Holmes was obviously the largest-prick actor in the film industry. 
(C’mon, you know somebody was going to!)
And someone already did (see post #15)
I’ll always think of him as the likeable Captain from Beverly Hills Cop, so he can play it both ways.
I started suspecting someone would around…oh…post 15 or so…
THAT is the dude I was thinking of when I saw the OP.
He was also party to what was perhaps the best exchange ever in an Adam Sandler movie (I know, to some people that may not be saying much, but still).
Shooter: I eat pieces of shit like you for breakfast.
Happy: You eat pieces of shit for breakfast?
Shooter: What? Uh…Nooooo!
I know he was alluded to, but someone should mention **Malcolm McDowell **by name. I guess I will!
Alessan, William Atherton’s character did not rape and kill Diane Keaton’s character in Looking for Mr. Goodbar. He didn’t even have sex with her, unlike Richard Gere’s character. It was Tom Berenger’s character that raped and killed her. In fact, William Atherton played a nice guy in that film, although the character was a little clueless.
Though not as despicable as Itzin, these guys can have you hoping they get their just deserts within minutes of their first appearance on screen:
And even when he’s a “good guy” Bruce Dern can make your skin crawl.
Does anybody else remember Frank Thring?
Frank Langella makes a pretty good prick. His Richard Nixon was such a prick he got an Oscar nomination for it.
I’d say he got an Oscar nomination because he made him less of a prick.
Very different from Jeffrey Jones, who was busted on child porn charges.
Wow. I did not know that.
What, no love for that cocksucker Ian McShane?
My vote for evil actress is Mary Woronov. Really does the smirking sneer well, cf. Rock ‘n’ Roll High School and Eating Raoul. The Devil’s Rejects was great, Mary Woronov and Sid Haig. Sid is just plain nightmare fuel.
OMG, I* just *came home from watching Dylan Baker live on Broadway in the closing show of GOD OF CARNAGE, in which he played Alan, a man who pulls such assholic moves thoughout the show such as taking calls on his cellphone during the action. Loudly. He’s a slimy lawyer talking a shady pharmaceutical company through a PR problem with one of their drugs, and doesn’t care who knows it. Finally, he has slicked-back hair, which screams assholery no matter what these guys think.
In real life, though, he’s a nice guy and a fine director and married to a sweet, talented singer and actress named Becky Ann, who I’ve seen in shows many times.
Nixon was a prick and he was portrayed as such in the movie. IMHO. YMMV, BIBW (But it’d be wrong.) 
Here’s what I mean. I am 35 years old. Nixon has always been a stereotype. Langella portrayed him not only as a bad guy, but also human and frail. He showed that Nixon was so desperate to rehabilitate himself, that he got in bed with a character like Frost.
He’s still a douche in the film, but he’s not a cartoonish villain out of central casting.
Glenn Shadix has a near monopoly on the suave gay prick. (He used to be rotund but he’s lost a lot of weight in recent years.)
To me Jason Alexander is only believable when he plays pricks. (Personally I considered George Costanza one.)
Prior to the lovable daffy Rose on The Golden Girls Betty White specialized in playing she-pricks and still does a good job at it. Her appearance on Ugly Betty as a version of herself (one who’d blown her Golden Girls money at casinoes, played the sweet old beloved icon when cameras were rolling and turned into merciless self serving biatch when they were off) was hysterical as was her Sunset Blvd parody episode on The John Larroquette Show.
Larry Miller …really?