The Fearless Hyena (1979)

Shing Lung (Jackie Chan) is a youngster, living in a remote village with his grandfather who teaches him Kung-Fu. He keeps getting into fights, even though his grandfather warns him not to show their Kung-Fu to others. Lung, though, is tempted by some thugs he beat up to act as the Master of a Kung Fu school. This school's name apparently spreads far, as an old enemy of Lung's grandfather shows up and attacks him. Lung goes on training with the help of another member of the old gang, until he can eventually get revenge.