The Perfect Killer(1977)

Betrayed by his girl and best friend, thief Harry Chapman takes the fall for a racetrack robbery. While in prison, he is offered a chance to participate in an escape plan. What he doesn't know is that once he is on the outside, the group responsible for the prison break has Harry in their debt and they use him as a hit-man. Naturally, he grows tired of the job and splits because he is hellbent on getting revenge on the former partners. So the mob puts young hit-man Luc on Harry's trail.