Zucco

Zucco is a Gotham City crime boss.

History
Zucco ran a protection racket, and tried to extort money from Jack Haly. After Haly refused, Zucco had his men sabotage the circus rig. Victim of this revenge were the Flying Graysons, the trapeze act. Dick Grayson, the youngest, lost all his family, and eventually became Robin. One of his first acts in costume was bring Zucco to justice.

Background in other meda
In current continuity, Tony "Fats" Zucco was a mid level crime boss working for the Falcones, who wanted to use the circus to smuggle contraband across state borders.

His appearance in Young Justice seems to be inspired by how he looked in The Batman, with a lean face and chewing a toothpick.