Jim Shooter and Wayne Boring introduce a less successful foe for Superman, Grax, in Action 342 (Oct. 66).
The story opens out in space, as Grax runs in to Brainiac. He claims a higher intelligence level than the android, and bests him in their first encounter. Grax is heading to Earth to kill Superman, after Superman destroyed his criminal empire.
Grax sticks a bomb belt on Superman, so powerful it will destroy the Earth when it explodes. Superman has a day to try to get rid of it, but it withstands anything and everything.
It’s somewhat interesting to see Superman’s increasing desperation, when the belt seems as indestructible as he is.
In the end it is Brainics who comes to Superman’s assistance. Both because Grax bested him, and because he wants to defeat Superman himself, Brainiac gives Superman the information on how to defeat Grax. It requires a giant magnet, as you might have guessed.
Superman and Brainiac congratulate each other on their defeat of Grax, who vows to return. He does, and in this book, but about six years down the road.