Pied Piper - Suicide Squad: Kill the Justice League

A friend of Captain Boomerang and former costumed supervillain, Pied Piper has since left the Rogues and gone legitimate. 

Back when he was working with the Rogues, he attempted to use his mastery over hypnosis and soundwaves to hypnotise Superman into joining them. However, this plan was foiled by the Man of Tomorrow, who had overheard him planning the scheme. It was after this defeat that he decided to retire.