Badge 373 (1973)

When his partner is killed, tough Irish detective Eddie Ryan (Robert Duvall) vows to avenge the death, whatever the cost. As he begins unraveling clues, his behavior becomes so outrageous that he’s obliged to turn in his badge, but the experience only emboldens him. Ryan eventually learns that his partner was caught up in a Puerto Rican gun-running scheme masterminded by a crook named Sweet Willie (Henry Darrow), who wants to foment revolutionary war.