Soul Brothers of Kung Fu (1977)

Two kung fu factory workers come to the rescue of a young black kid who is attacked by some bullies that work for the boss. As a result the boss, not wanting to lose face, starts to harrass them, making it hard for them to find work.

As time goes on, Li, who becomes the black kid's kung fu teacher, goes into tournament fighting (in order to make enough money to marry the girl that his friend also likes), whilst his friend goes down a different road - where he gets into a fight over a betting refusal and slowly falls into depression. The boss, seeing this, turns him against Li with the subtle use of a sexy bar girl. He also employs some specialists to rape and murder Li's girl, and also attempts to kill the black kid and Li. Li is nearly killed, but returning to health, he goes into kung fu revenge mode against the specialists and finally the boss himself.