I found Hans Landa to be despicable. A self-proclaimed “Jew Hunter” who after all of his evil…betrays the Nazis and tries to secure an American citizenship and stipend/salary from the US government.
When we learn that he isn’t even loyal to the Nazis…it just seems so much even more despicable. Evil just for self-gain all the time.
Max Cady in each of the versions of Cape Fear (Robert Mitchum or Robert De Niro). Yes, he’s pure evil, but at no point in the movie do I think he is anything but despicable.
Hollis Mulwray (Chinatown) was a pretty horrible character. The scene at the end of the movie where he is leading his grand/daughter away into the night makes your skin crawl.
Flap Horton in Terms of Endearment was a weak, childish, philanderer. He didn’t get anyone killed, he didn’t kill anyone, he was just despicable. Never be a Flap.
Bernie Bernbaum (John Turturro) is despicable in Miller’s Crossing. He’s about as bad as William Macy in Fargo or Paul Reiser in Aliens — maybe a tick below,
Or Joanna Kramer in Kramer vs. Kramer. Abandons her young son, then goes to snatch him back after he’s happily adjusted to life without her, with the aid of sleazy legal tactics.
Bruno Antony - spoiled, psychotic playboy in Strangers On A Train.
Phillip Vandamm in North By Northwest (“This matter is best disposed of from a great height, over water.”)
Somewhat in the vein of the OP, Paul Giamatti’s character in Sideways steals cash out of his mother’s sock drawer. That’s rather despicable behavior. The movie then tries to portray him as a somewhat sympathetic character, but it’s kinda too late.
I place Big Dan in a bucket with Homer Stokes — rotten and murderous but not slimy and despicable. Opinions vary. And although Stokes and Teagues are horrible, they’re are presented as somewhat comic (as is George Nelson, the cow killer).
Bernie blackmailing his savior is loathsome, as is his pragmatic murder of a lover (which he later chuckles about).