Not only was A Fistful Of Dollars a breakthrough for Clint Eastwood's career, it also shattered one major taboo regarding movie violence. Eastwood's early career was filled with small, sometimes uncredited parts in various movies and TV shows, but after filming 1958's "lousy" Western Ambush At Cimarron Pass, he considered quitting the business entirely. Eastwood's fortunes changed when he was cast as Rawhide's Rowdy Yates, but it was A Fistful Of Dollars that truly made him a star. This low-budget Italian was an unofficial riff on Yojimbo, and its success practically led to the creation of the Spaghetti Western subgenre.

https://screenrant.com/fistful-dollars-movie-violence-rule-break-gun/