Stiletto (1969)

"What some people dream of...the Harold Robbins people do. They do it all in Stiletto."

A rich, jet-setting playboy has a secret life: he's also a professional Mafia hitman. When he decides it's time to retire from that life, he finds that his former employers don't like the idea that someone who knows so much about them won't be under their control anymore, and decide to send their own hitmen to eliminate him.