AJ will always be the character I loathe the most, but he was a 100% boon for the story as a whole. Tony's lack of meaningful fatherhood directly results in a son who's lazy, unmotivated, and unfit for a life in either the world of wealth he was born into, or the criminal life his father dominates. Some of Tony's greatest displays of hypocrisy and misplaced sense of values are shown through his relationship with AJ.