To get a more candid reaction from actress Cathy Moriarty, Raging Bull director Martin Scorsese didn’t warn her that Robert De Niro (as her husband, boxer Jake LaMotta) was going to slap her during an on-screen argument. She was surprised, but was anyone else? From Travis Bickle in Taxi Driver to Max Cady in Cape Fear to Dwight Hansen in This Boy’s Life, De Niro’s characters are landmines. The acting heavyweight has used that menacing quality to great effect, even in later, lightweight fare like Meet the Parents. His latest is another comedy, The Intern, opening September 24.