Hidden Strength.

Other demon kings can create barriers that will be able to match the defense of his body but they will need to actively put up that defense while he doesn't. It means he didn't need to worry about the Celestial of Metal's attacks and the joint attacks of all ten Celestials. He could have just waltzed through them but he hid his strength. He can go all out now that he is covered by the cloud of Chaos energy. No one will see what he is capable of. Even his victims won't be able to see. And if they can, they won't be telling tales after he is done with them.

He practically ripped the three Celestials apart. He dug his hands into their bodies and pulled their Godhoods out from within them while they were still alive. They tried to resist but it was all futile. They were no more than petulant children to him. He ripped out their hearts as easily as taking candy from babies. He watched the life leave them as their bodies fell apart.