Harrison Ford in Return of the Jedi and Bradley Cooper in Hangover III. They both look unhappy and had to fulfil contractual obligations.
Wesley Snipes - Blade III. They had a cooler idea for III involving waking up in the future and finding vampires rule the world, farming the remaining humans like cattle but they went with this film instead.
Donald Pleasance - Halloween 6. He looks very unwell and died shortly after.
William Hurt in Avengers Infinity. He looks like he'd rather be elsewhere. (He was an abusive prick to Marlee Martin so screw him.)
Gene Kelly in Viva Kenieval. With no musicals for him to dance in during the 70s he plays a drunken, absent dad in a dumb Evel Kenieval flick.
WHO else is worthy of pity?