Blood for a Silver Dollar (1965)

Giuliano Gemma plays a confederate soldier who returns from the war to fight one at home. Unbeknownst to him, his brother has become the infamous gunfighter "Black Jack" to defeat the local bullies. Gemma agrees to ambush and kill Black Jack, only to discover too late who the outlaw really is. With vengeance in his heart he turns on his employers, who then shoot him.