70s movie w/ old man, hero, and kid

Don't know the name obviously and only recall scenes. Old man teaches this drunk (hero) how to fight a certain fist style. another character, the kid, learns how to fight monkey style. Big ending is prompted by the killing of the old man by an enemy. The hero and kid fight the bad guy.

Every time the bad guy gets stabbed, it doesn't penetrate the skin. This stumps the hero and kid and soon they realize it's because of a pendant he's wearing around his waist. Once they realize his weakness, they keep attacking the pendant to cut it off of him. once they do this, the bad guy is defeated.

The movie wasn't the best plot but the training was interesting and the ending was kind of sad and gratifying since they revenge the death of their master and friend.

anyone know this flick? I keep thinking the title of the movie is long since it names each of the main character by some trait. Gotta be from the late 70s. I could be wrong though.

I would give it 3 out of 5 stars.