My choice would be Eobard Thwane aka the Reverse-Flash or Professor Zoom, the Flash/Barry Allen's arch enemy and one of the darkest villains ever created by DC comics.
Thrawne is the living definition of spite and of the crazy fanboy having gone wrong, having been an obsessed fanboy of the Flash before becoming his nemesis and being responsible for all of Barry's suffering and tragedies in his life having murdered his mother Nora Allen and framed Barry's father Henry Allen for the murder of his wife, killing Barry's best childhood friend and tried to murder Iris too.
His other crimes include the murder and complete erasure via time travel of his own younger brother, the murder of his parents, having killed all the boyfriends of a girl he lusted for for had, and when she refused him he went back in time to traumatize her and scared her for life during her childhood causing her to become catatonic.
Professor Zoom's hatred of Barry and pettiness are such that his goal isn't of killing him but of making his life a living hell by every mean possible.
Deathstroke/Slade in Teen Titans was such a great villain, being very badass, very smart and manipulative, genuinely charismatic and creepy at the same time with him being the perfect nemesis to the Teen Titans and to Robin in particular, and being perfectly portrayed by Ron Perlman.
Captain America's archenemy and a factual Nazi. He was originally working in Hitler's hotel as a bellboy, Hitler gave him the uniform and a skull mask.
America testifies how someone can stand as a symbol of good in a world of superheroes despite bearing no superpowers, Red Skull entails the opposite, intents wise.
Red Skull is a major sadist, killing people for fun and even considering torture as a form of recreation.
He killed Professor Xavier by removing his brain off and gain his psychic powers useful to his domination plus extermination plans, even planning to force Scarlet Witch to reshape reality to his will until he was killed.
Fam, The Falcon and The Winter Soldier episode 4 was ill af
Ayo was savage af, my boy Bucky didn't deserve that The Dora Milaje are just built different. I want a Dora Milaje series so bad
Honestly, fuck that fake Capt. America, boy was just jarrin and chatting shit all through the episode. He got humbled by the Dora Milaje real quick
I need to find a day to re-read or get back into comics.
Though best villains for Marvel and DC, no better than Dr. Doom (Marvel) and i would have to pick between a few characters from DC like Batman who Laughs, Sinestro, Deathstroke, Red Lion (a better no shits given version of the crap known as Black Panther) and Reverse Flash (Eobard Thawne)