Call me vicious, call me sadist, but my personal favorite "Twilight Zone" episodes (favorite movies in general, in fact) are the ones where the protagonists are pure evil. Not just committing evil deeds, but evil to the bone, with rotten personalities and deliberately dedicating their lives to mentally torment others. Someone like Uncle Simon in this TZ-episode with the same name, for instance, and I couldn't think of an actor more fit to depict him than Sir Cedric Hardwicke ("The Hunchback of Notre Dame", "Ghost of Frankenstein")
The idea behind "Uncle Simon" is preposterous, but delightfully entertaining. Old and sickly Simon Polk is a loathsome tyrant to his niece Barbara, who lives in with him and spends her days acting as a nurse and taking care of the household. Uncle Simon continuously insults and humiliates her, but the woman literally awaits his death and the inheritance. Still, only after his passing, it will become clear to Barbara why Uncle Simon spent so much time in his laboratory in the basement.
You could easily state that writer/creator Rod Serling intended this story to be a complaint towards typically human vices like greed and selfishness, but I prefer to see it simply as a pitch-black comedy and a showcasing of Sir Cedric Hardwicke's amazing talent for playing ultra-villainous roles.