The Departed (2006)

Jack Nicholson's Frank Costello turns every meeting into an unstable social test. The humour is abrasive, but the crucial pressure is never knowing whether his apparent amusement means permission or danger. In The Departed, that volatility makes maintaining an undercover identity feel exhausting. Choose it for a crime boss who contaminates the working habits of the people around him, within a busy ensemble whose betrayals matter more than any single flamboyant turn.