Yes he did. And he did it with a steak knife and their own guns. I believe it was 12 gambinos.
12 gambinos isn't a whole crime family.
John Wick took down the head family of a russian crime syndicate. He destroyed his money and the files he was using to blackmail everyone.
Then made the man basically kill his son to live, then killed the man and his lawyer anyway.
Then went to his brother at the beginning of the 2nd movie and got his car back after killing the muscle for his crew.
Then killed a principle leader of the high council, stayed alive from a worldwide contract on his head.
The accountant aint fukking with that.