|The Ladykillers (1955) [Harry a.k.a. Mr. Robinson]: Bludgeoned to death (off-screen) with a wooden plank by Danny Green; we only see Danny chase Peter behind the building. His body (just his feet, actually) is shown afterwards when the other gang members prepare to drop him into a passing train from an overpass.
Lolita (1962) [Clare Quilty a.k.a. Dr. Zempf]: Shot repeatedly by James Mason in Peter's mansion; Peter is hiding behind a painting at the time of the fatal shots.
Dr. Strangelove: Or, How I Learned to Stop Worrying and Love the Bomb (1964) [Group Captain Lionel Mandrake/President Merkin Muffley/Dr. Strangelove]: Playing a triple role, all three of his characters die (along with everybody else in the world) when the Soviets' doomsday device is activated.
Casino Royale (1967) [Evelyn Tremble a.k.a. James Bond, 007]: Killed in an explosion (along with almost everybody else in the movie) when Woody Allen accidentally blows up the casino; he is seen as an angel floating on a cloud afterwards.
Trail of the Pink Panther (1982) [Chief Inspector Jacques Clouseau]: Killed in a plane crash (off-screen) when his plane disappears at sea. (Peter's part consists entirely of recycled and unused footage from before his real-life death.) This film does not confirm whether or not the character is actually dead or simply missing, but it was finally confirmed in the 1993 sequel Son of the Pink Panther.) (Thanks to Robert)