If not a villain, then some annoying character who got what they deserved. My number one favorite is from:
DIRTY HARRY - Scorpio, the killer/child molester played by Andy Robinson. Harry dishes out some serious punishment on this guy. Stabs him, shoots him in the leg, then tortures him. Shoots him again in the shoulder and finally shoots him dead at film's end. Sweet.
1. FIRST BLOOD - Galt, the A**hole cop who falls out of the helicopter.
2. NIGHT OF THE LIVING DEAD - Harry Cooper gets shot by Ben, then his own zombie daughter chews his arm off!
3. BACK TO THE FUTURE - Biff is humiliated when the class wimp punches him out. Satisfying.
Perhaps at the top for me would be John Cassavetes getting blown to smithereens by Amy Irving's mind power in De Palma's "The Fury" while Mr. Williams provides musical hysteria (the shot is repeated 13 times in slow motion from various perspectives).
Also the demise of Mr. Lorre in "M" is pretty wonderful. As is Mr. Welles being chased to death in the sewers in "The Third Man" or collapsing as a grotesque heap of flesh in the mud puddles of "Touch of Evil."
Old Barnaby having his bride Bo-Peep surreptitiously replaced by Stannee Dum in BABES IN TOYLAND. Revenge is Sweet. (He later gets whacked in the chest with a roll of toilet paper and then knocked out by being hit on the head with a balloon, but the wedding was the best).
Classic Disney animation had a way with this -- so many wonderful moments! Cruella De Ville going to pieces in her automobile, Captain Hook and the crocodile, the witch chased on mountainous rocks in "Snow White". Also, as a kid, the conclusion of the Japanese animated film, "Shonen Sarutobi Sasuke (Magic Boy)", wowed me -- the hero boy chases and overcomes the water witch and slowly destroys her until she crumbles apart as a ghastly white, fleshless, skeleton! Great stuff.
The end of the first "Indiana Jones" movie is excellent when the Nazis open the Arc Of The Covenant, look at the spirits, and implode. For its day the special effects of physical demise were astounding... and gratifying to see the villains done in so uniquely/effectively/completely.