Yomi Hellsmile. Bastard is a rude and offensive jerk to enemy and ally alike, never once trying to hide his murderous and selfish intentions from anyone. He even cusses out his own superior as casually as he breathes air.

Art the Clown, when he isn't graphically and painfully killing people, he goes out of his way to be an annoying nuisance to everyone around him.

Carnage. He's a card-carrying mass murderer and a psychopathic serial killer. He does have some minor moments of being a faux affably evil, but that's really rare. He's always darkly sarcastic and disrespectful.

Junko Enoshima. She tends to unpredictably switch between different personalities, each of them more obsessed with despair than she already is.

Probably the Qu's they don't fake affability in the slightest they go in mess everything up and go that's it.