Albert Barnes Commentary 2 Samuel 19:5

"And Joab came into the house to the king, and said, Thou hast shamed this day the faces of all thy servants, who this day have saved thy life, and the lives of thy sons and of thy daughters, and the lives of thy wives, and the lives of thy concubines;" — 2 Samuel 19:5 (ASV)

Had Absalom gained the victory, it is likely that, according to the custom of ancient eastern despots, he would have sought to secure his throne by killing all possible competitors (Judges 9:5; 1 Kings 15:29).