Samurai Jack: The Premiere Movie (2001)

A small boy is sent away from his village. He is to be trained as a samurai warrior and return to fight the evil shape-sifter, Aku, who has wreaked havoc throughout the village. His skills honed, the warrior attempts a return to his home, but winds up in a future time landscape. Here, the locals call the stranger, a sort of Dirty Harry kung fu loner, "Jack" and assist him in his path homeward. This is the original feature length presentation that kicked off the SAMURAI JACK phenomenon on the Cartoon Network.

Source: TMDb