Wu zhao shi ba fan (1979)

A "Dragon Claw" master returns from Manchuria where he became a traitor to China. He's after the coveted Dragon Claw Golden Tablet that will force people to bow down to him. He challenges the Grand-master who has a checkered past of his own. The Grand-master happens to suffers from a terminal chronic injury related to his evil past. The traitor kills the grand-master, causing his wife and son the go into hiding. The wife seems to really be the Dragon Claw master in the family and she vows to train her son the kung fu secrets. The son finds that one of his friends has learned a strange style of kung fu from a filthy medicine man. The son seeks him out to improve his kung fu and defeat the traitor.