No matter the part, he always seemed at ease and in control, whether playing a Mexican bandit in the 1960 western “The Magnificent Seven,” a bumbling clerk in Ionesco’s allegorical play “Rhinoceros,” a henpecked French general in Jean Anouilh’s “Waltz of the Toreadors,” Clark Gable’s sidekick in “The Misfits” or a Mafia don in “The Godfather: Part III.”