Jesse Plemons, with his boy-next-door looks, has a great talent playing sinister characters. What makes him particularly unsettling is his ability to bring a quiet, understated menace to his roles. He doesn’t rely on exaggerated expressions or dramatic gestures; instead, he conveys evil with a calm, almost soothing presence that’s deeply unnerving. His performances are full of tiny, barely noticeable quirks that subtly reveal the depths of his characters’ malevolence, adding layers of complexity to his portrayals. I’ve enjoyed all the parts I’ve seen him in. Chilling.
Going for a less known actor, I always enjoy Michael Wincott - it’s probably his voice, which is dark, raspy, and intimidating, or the fact that a number of times he’s played someone completely For the Evluz, such as in The Crow, or the Count of Monte Cristo.
In terms of names no one had mentioned, I cannot believe (per a quick alt F) no one has mentioned Tim frikkin Curry. 
Although, in many cases, it’s an evil character with a hint of camp, I still love watching his performance as Darkness which is almost entirely free of such. Again though, his voice is a large part of all his portrayals.
William B. Davis
Lee Marvin
Malcolm McDowell
Peter Stormare
Excellent choice. The Cigarette-Smoking Man was a outstanding, thoroughly creepy villain.
Wrong actor. Mads Mikkelson did a much better job.
At that: Jeremy Irons. Yeah, if you want him to camp it up as a scenery-chewing villain, you’ll get your money’s worth — but if you just want a guy with that voice to casually put aside every concern other than being one step ahead of everyone else, he’s on it.
Lifting a trivia item from the IMDb entry on The Lion King (1994):
In the first conversation between Scar and Simba, Simba comments to Scar, “You’re so weird…”, to which Scar retorts a cryptic “You have no idea…”. This is the same answer spoken in similar fashion by Jeremy Irons in Reversal of Fortune (1990), after his lawyer tells him “You are a very strange man.”
I recently had a whole thread on if Giancarlo Esposito ever played a good guy. He has, btw, but is so, so good at being bad.
He won an Oscar for it too?
Richard Boone, especially in Big Jake, although he also played a good guy as Paladin in :Have Gun, Will Travel".
While not techically evil, per se, R. Lee Ermey could play a helluva bad guy/hardass.
James Cromwell as Dudley Smith in LA Confidential, particularly since he was not always obviously evil. But when needed, his eyes were as cold as the infinite depths of space. He also played Farmer Hoggett in the Babe movies - quite the range!
Lionel Atwill
Rudolf Klein-Rogge
Robert Mitchum – Night of the Hunter (1955); Cape Fear (1962)
Wolfgang Preiss
Robert Ryan
Henry Silva
Erich von Stroheim
Max von Sydow
Orson Welles – The Third Man (1949)
David Tennant.
If you don’t believe it from watching him in “Jessica Jones,” check out his performance in a movie called “Secret Smile.” He was chilling.
Michael Emerson, for his roles as Benjamin Linus on Lost and Leland Townsend on Evil.
Speaking of actors playing a villain named Leland, I can’t see him as anything other than a villain after watching him play Leland Palmer on Twin Peaks. He guest starred on an episode of Psych and I immediately thought he must be the killer. He wasn’t, but it seemed that way for most of the episode.
He showed up for an episode of Star Trek as a member of a species described as being “quite peaceful and highly rational — which is not surprising, considering how closely their evolution parallels Vulcan.” And so, complete with pointy ears and a ‘Spock’ haircut, cue Ray Wise as the guy who — shoots Captain Picard.
Jack Cassidy played the killer on three Columbo episodes, to great effect.
I just watched Trap and Josh Hartnett is great as the villain. I got the sense that he was a sociopath who was faking emotions well enough to get by but also with a couple of moments of real emotion mixed in here and there. Fantastic performance the whole way through.
John Hurt as Caligula in I, Claudius portrayed a psychopathic killer so well it all but freaked me out.
Zone of Interest came to the streamers so I watched it, and I have nothing to add that hasn’t already been said months ago. (Yes, the next day I was cleaning the kitchen and folding laundry asking myself “could I do this while people are being gassed next door? And Stanley Kubrick would approve of how they shot this film, etc.)
But, as to this thread topic, it was a signal that German actors should now assume the responsibility of accurately portraying Nazis, not British actors. Brits like Olivier and Kenneth Branaugh filter the Nazis through Shakespeare, with his wealth of insight into mendacity. But Shakespeare never had to wrap his head around anything like the Nazis. Shakespeare never wrote for rats, but Brecht did.
Kim Coates. oozes evil from every pore, whether “lead” bad guy or part of a group.