We do see him giving Mannheim this giant (full-page) wedgie: The resulting battle is so epic that we can’t even see the whole last part (it happens underwater), presumably because DC can’t print a comic depicting Superman breaking the Geneva Conventions multiple times per second. Mannheim gets covered by some sort of rocky armor ( here’s an animated dramatization) and goes head to head with Superman.
It’s at this point that we find out the secret origin of Mannheim’s legendary ugliness – he’s not human, but an alien from Apokolips! Which I probably spoiled for you at some point, but please act surprised anyway. However, Superman saved the best part for himself: now that he’s shown his fiancee who’s the better reporter and can finally use his powers again, he personally goes after Intergang boss Bruno “Ugly” Mannheim.
Thanks to Clark’s thievery, Intergang hideouts are raided by the cops all over Metropolis and hundreds of goons are arrested. Turns out that, all these years, all Superman had to do to get rid of Intergang was steal the briefcase of Intergang’s careless second in command, Gillespie, and publish its contents in a newspaper. THE END OF INTERGANG! Superman finally gets off his ass and takes care of that pesky criminal organization operating from his city – or, more accurately, Clark does all that, since (per a bet with Lois Lane in Superman: The Man of Steel #4) he has to break a story without using his superpowers.
