The Good Guys and the Bad Guys (1969)

Marshal Flagg, an aging lawman about to be retired, hears that his old nemesis, the outlaw McKay, is back in the area and planning a robbery. Riding out to hunt down McKay, Flagg is captured by McKay's gang and finds out that McKay is no longer the leader of the gang, but is considered just an aging relic by the new leader, a youngster named Waco. Waco orders McKay to shoot Flagg, and when McKay refuses Waco abandons both of them. Flagg then takes McKay back to town only to find out that he has been "retired," and when he sees how clueless and incompetent the new marshal and the city fathers are, he persuades McKay that it is up to the two of them to stop Waco and his gang from ravaging the town.