John Boyega, Kelvin Harris Jr., or Damson Idris
5 years ago I would've probably said Donald Glover but he's a little older than the Mr. Terrific I imagine DC would go with on the big screen since he's almost 40; also iunno if he's the type to sign on to a franchises like that. however, if they wanted to go the route if a comfortably experienced Michael I'd be down for him to take the role still.