Gus Mascola was a merciless mobster trying to take over many black neighborhoods in Queens in Shaft's Big Score (1972), the first sequel of the Shaft series.
He was portrayed by Joseph Mascolo.
He is an exploiter who only spares lives if they are of any use to him. He tells Andrew, his pal and partner, to spare Kelly (a traitor claiming to be on John's side), but that is only to take advantage of him. The only reason he doesn't kill Kelly right away was because he, as Mascola said was "the key to Queens". He's affably evil to his men and family.
If anyone got Mascola angry, we could see his ugly side. We see his ugly side in three scenes. The first is when Mascola has his men beat John up, when Kelly lies claims, wrongly, he's working for Bumpy. The second is in a nasty fight he has with John and Willy, in which he racistly belittles John by calling him a "boy". In addition to his exploitive side, he is shown to abusive to his wife. In one scene he threatens to hurt his wife. The last time we see his ugly side is when he shoots Kelly. The next time we see him is right after in an exciting chase sequence that takes us from a graveyard to a ship deck, both in Queens. We see one final fight between him and John and John leaves him to explode in the boat.