Beautiful Virginia Mayo in The Best Years of Our Lives. I’m sure she was a nice person in real life, but in this movie she’s what my dad called a “floozy.” (I’d go a bit farther than that, myself.)
I often get the feeling that Anthony Hopkins might not really be acting.
The day ain’t over yet.
Ronny Cox is quite good at playing murderous corporate assholes. See: Robocop and Total Recall.
Perfect response.
Indeed. Also see Claire Trevor in Murder, My Sweet, and Jane Greer in Out of the Past. (Noir in general provides many actresses who “do a good job of playing evil…” as the thread title puts it.)
Barbara Stanwyck in Double Indemnity is about as evil as anyone can get. A lying, manipulating, emotionless, sociopathic multiple murderer.
How about David Boreanaz?
As Angel, he was mostly mopey and broody, but with occasional moments of true darkness (locking the lawyers in with Darla and Drusilla), but as Angelus, he just goes over the top in gleeful evil.
Dabney Coleman was always good as an egotistical jerk especially in his series Buffalo Bill.
Speaking of Buffalo Bill there is Ted Levine playing the serial killer with the same name in Silence of the Lambs,
and speaking of serial killers Michael Rooker playing the title character in Henry: Portrait of a Serial Killer.
I was not a fan of Boreanaz. I find him a wooden actor, with only mediocre comedy chops, and not especially impressive as a villain. De gustibus and all.
The best the last actor not mentioned so far, in my opinion, is Walton Goggins. He chewed scenery as the ghoul in fallout. He did the best he could in Ant-man. But as Boyd Crowder? Holy smokes, one of the best villains in fiction.
Which makes me think how much I’d love to see a PG-13 Treasure Island, with him as Long John Silver.
No mention of Hans Gruber?!
Jeffrey Dean Morgan - Mostly known for Negan in The Walking Dead, but also Joe Kessler in The Boys and The Comedian in Watchmen.
I’m embarrassed to say I recognize Mr. Goggins mostly by his dental work. “Hey, honey, it’s that guy with the teeth, again!” “Is he shootin’ up Waylan again?” “Any minute now!”
Hell, he was creepy all the way back to In The Heat of the Night when he kidnapped Mrs. Tibbs and did something nasty to himself.
What a badass!
One of the scariest psychopaths in movie history is Ben Kingsley’s Don Logan in Sexy Beast. Mind you, Ian McShane as his boss, Teddy Bass, is not far behind him. It is a terrific movie but not a very comfortable viewing experience,
This is who I came in to mention. Did you see him in Babylon 5? His character was Brother Edward, a gentle natured monk. Turns out he had a mysterious past.
Since people are mentioning Babylon 5 villains I would like mention a few for its dueling show Star Trek: Deep Space Nine:
Marc Alaimo as Gul Dukat
Jeffrey Combs as Weyoun and Brunt
Salome Jens as The Female Changeling
Has the name James Woods been invoked yet?
What makes him great as an evil character is that even when he plays a sympathetic character, as in Salvador (great movie by the way) he plays the role as the scummiest, most dishonest weasel of a sympathetic character imaginable. Of course he’s also played his share of out and out rotten to the core villains as well: Roy Cohn, for one, and the NASA scumbag in Contact.
Also qualifying him is the role he plays as James “MAGA FOREVER” Woods in real life, of course.
Say it isn’t so, Joe… James Woods is MAGA? 
Even his voice acting runs the gamut from Hades (in devil-as-businessman mode) to Batman’s evil counterpart (in kill-lots-of-people-in-cold-blood mode).
(No, more people than that.)