Originally posted by JBLif it was prevented from release by Superman why create another magnetic field? And once Superman’s GL create a magnetic field Superman even states that the pressure was lessened.
Superman caught that black hole before it released and kept it from releasing very simple. That's why he was only talking about pressure because that thing was trying to release.
Mnemon didn’t stop trying to release himself while in Superman’s hand. Why would it stop? It was released as soon as Superman got it and then the gravitational pressure was insane from the start. It only lessened once Superman and Gl created their own magnetic field. Right there in the comic, even albi understood this.