In Fall Out Toy Works, Baron makes himself out to be perfectly civil in his business dealings and serves as a mall Santa for orphaned kids...but it's very much an act and only the most oblivious would be fooled.
Get Jiro!: Unlike the Wicked Cultured Bob, Rose and her husband Jerry are much rougher when it comes to their mafia-esq practices, often imposing Cool and Unusual Punishments for minor sleights, like killing one of their own chefs and feeding their bodies to their pigs for serving a tomato dish in January. It's even stated that they tend to change whatever "cause" they try to represent constantly, using positive brands (environmentalism, civil rights, etc.) purely to draw in business.
Judge Dredd: Judge Death, an undead executioner from another world, has a habit of happily greeting his victims before squeezing the life out of them. He's also a lot more prone to bits of dark humor and Pre Mortem One Liners than his three associates. Must be the Slasher Smile.
Mr. Hyde, whilst not evil, is a perfect example of this with his Blue-and-Orange Morality, frequent dog shooting, and his Psycho Supporter attitude. The most notable example of this is where he maintains a polite demeanor, observes the London cityscape, and discusses how lucky and chipper he feels whilst he pummels and rapes Griffin because he assaulted Mina. This is then further added to in a later scene, where he maintains a conversation even when he notices that he is covered in the gradually appearing invisible man's blood (due to his recent demise). He even deserves bonus points considering that, upon seeing the horrific aftermath of the above event, Captain Nemo tries to kill Hyde in disgust whilst Hyde continues eating his dinner. Of note, he appeared to be pantomiming eating dinner up until then, because the main course was Griffin's leg which, like his blood, only became visible after he died.
In Volume 1, Professor Moriarty displays the honour and good manners of a Wicked Cultured villain dealing with a Worthy Opponent in the Great Game ... as long as he's winning. When the cracks start to show, he'll maintain the appearance, while dropping snide criticism at his foes. When he's really not winning, he shows he's Not So Above It All by screaming abuse at them. He does it in the Flash Back to Reichenbach, and he does it again at the climax.
Tartarus speaks in a very smooth and relaxed tone to his opponents. He's also, in truth, a vicious psychopath who intends to rip Europe apart so he can rule the ashes.
Eustace Morley is a charming plantation owner and ever the gracious host who's also a vile slaver and smug bastard.
In Peter Cannon: Thunderbolt (2019), while Thunderbolt isn't so much affable as calm and insufferably smug, he maintains a facade of politeness and good humor. He's a virtual god, and believes (mostly correctly) that he can obliterate anyone he chooses on his own territory, at whim.
Requiem Vampire Knight: Otto von Todt is so jovial and friendly at times (primarily around Heinrich) that you almost forget that in life he was a sadistic Nazi concentration camp guard. Notably, he gets a lot more openly nasty when Heinrich hooks up with his Jewish girlfriend Rebecca again in Résurrection.
Dr. Eggman himself is far more murderous and irredeemable than his video game counterpart, but has nearly all the same whimsy and charm; whether he's enslaving, destroying, or just being cruel, Eggman is sure to be having a fun time. Best shown when he surgically repairs Lien-Da after she's blown up by the Iron Queen and explains in cheerful detail the Explosive Leash in the cybernetics, complete with a Cheshire Cat Grin.
Eggman: If you or any of your Echidna buddies cross me... you're all going up like a fireworks festival. Very festive. Very colorful.
Star Wars: Age of Resistance shows that General Hux can feign niceness when he wants to. When he and Kylo Ren were marooned in a remote planet, he manages to befriend a former Alderaan guard who had lived there as a hermit for over 30 years and won the man's trust enough to let them use his communication device to contact the First Order. Once the First Order arrives, Hux promptly betrays his benefactor: killing his animal companions and destroying his communication device while abandoning him on the planet, which Hux intends to use as the Starkiller Base's target practice.
Decepticon Justice Division leader Tarn quotes literature and plays fine music while he and his teammates torture you to death. His preferred method of killing isn't even violent — he's capable of modulating his voice in a way that lets him destroy your soul. Of course, that's only after his buddies have run out of ways to mangle you.
Pharma starts out being friendly and likeable. As it goes on, though, it turns out that he's come to see murder as a joke and torture as a fun little peccadillo.
First Aid: You're smiling. Everything you did at Delphi—all those patients you killed — and you're smiling? Pharma: I know, I know—I'm incorrigible.
