The Hired Killer (1966)

Hit-man Clint Harris has one more job to do before he can retire. He's to kill an ex-employee who has become a snitch for the police. At first Harris refuses, but when his brothers assassinated, he's forced to accept. He's assigned an assistant, whom he teaches the ropes as they pursue their prey. When a beautiful woman identifies the target, it turns out it's the wrong man. As bodies pile up as he wonders whom he can really trust.