Superman couldn't break from the grip of a huge Kryptonian Dinosaur. He was still depowered and couldn't fully recharge his cells before the fight. He went easy on it and hit it just once with a punch that would topple a small mountain.
The cells of the creature were decaying and the explosion finished it off.
Even by every stretch of imagination, I can't see how this can be a low showing for Supes. Fighting a Zombiebada from Krypton, while his cells weren't reacharged after he bench pressed the weight of earth for 5 days without the Sun...
It's actually a high showing and supports the bench pressing strength...