Richard Burton, Peter O'Toole and Brian Blessed.
Burton, fab in Beckett, Raid on Rommel, Cleopatra, Night of the Iguana and 1984. I remember more for Medusa Touch and Where Eagles Dare - a great film, but his performance was terrible!
O'Toole again great in Beckett, Lawrence of Arabia, the Lion in winter, then Supergirl, the night of the generals (insanely good cast, mediocre film), Caligula (!), king Ralph...............
Brian Blessed was amazing in I Claudius, my family and other animals, the Black Adder, and Return to Treasure Island then Flash Gordon, dick and dom, Peppa pig!
As I say, great actors who like most people in their profession have appeared in some absolute turds.