Lol Superman is not broken. He's pretty good but not TOO good. He's kind of a jack of all trades, master of none type of deal, which makes sense. He can zone a bit, he can rush down a bit, he can mixup a bit, he can control the air a bit. But he has weaknesses.
Pretty much any special he does is full combo punishable outside of Breath on block. Flying Punch. Low Scoop. Point blank Heat VIsions, air or otherwise. Air Ground Smash. RIsing Grab.
F23~Breath isn't nearly as dirty as people think it is.
His crossup potential is virtually nonexistent.
His air dash can be AAd pretty easily.
He does fairly medium damage without meter unless cornered. MB Breath is pretty much required for 30+ percent, even with trait.
He doesn't have any TRUE 50/50 low/overhead game.
Superman is part fish, part dirt. He's a mudfish.