Frank Burns — M*A*S*H (1970)

Before the TV series made it a franchise, Robert Altman's MASH was a razor-sharp anti-war comedy — and Duvall's buffoonish, hypocritical Frank Burns was the perfect foil for its anarchic heroes. The role demonstrated Duvall's early mastery of comic timing and his willingness to play unlikeable characters without redemption. Elliott Gould later said Duvall's commitment to Burns made Hawkeye and Trapper's irreverence land.