The idea seemed to make sense when he was playing Heroclix.

Could a Veteran Luthor beat a Rookie Superman? That's Luthor's plan today, in 1974's Superman #282, "Lex Luthor--Super Scalp-Hunter!" Written by Elliot S! Maggin, pencils by Curt Swan, inks by Kurt Schaffenberger.

Luthor blasts Superman with an invisible ray that seems to do nothing, but when we next see Clark Kent he looks ten years younger, as he busts into Perry White's office to demand a staff job with the Planet. Perry assumes it's a gag, and plays along. Also for a gag: Steve Lombard snags Clark's jacket so it rips, but then immediately wonders what terrible thing is going to happen to him now. He's not really 'hip' to the notion of karma, but Superman had gotten him back multiple times.

Lex puts his test mission into play: three of his men attempt a mid-air hijacking, which is stopped by Superman, albeit in a more headstrong manner than usual: Luthor had de-aged Superman ten years or so, under the theory that a mature, experienced Luthor could easily take a wet-behind-the-ears, "barely out of his teens" Supes. His goal, Superman's scalp, may be a figure of speech, but at least one of his henchmen pictures Lex wearing Superman's hair. It would be invulnerable, right? That'd be protective, and stylish!

Although Superman is raring for the fight, he's not prepared for Lex's various weapons, including a gravity-caster that may have made Superman as heavy as the planet. Lex was going to use his "laser-knife glove" to scalp Superman, but ends up sinking with him, headed for the core of the planet! Surprisingly, Lex panics: he can't reverse the effect, or, apparently, just fly up; he's going to be dragged down with Superman until he burns up in the earth's core! Um...no: they were sinking pretty quickly, so Lex would either be crushed like a pancake already, or out of air, or maybe killed by the pressure change?

I thought Supes was playing possum, drilling downward himself to trick Luthor into giving him the antidote to the de-aging effect, but no. In fact, still affected by the gravity-caster, Superman has to have Luthor wrap up in his indestructible cape (which has to be snug, and crushingly embarrassing for Lex) then ride a lava flow back to the surface. Which wouldn't counteract any gravity effect at all, but we're running out of pages, so...Lex takes the 'L' for loss, while back at WGBS Steve is still terrified something is going to happen to him, so he's actually relieved to discover his pants have unraveled in front of Lois Lane. I'm not sure if his name on his boxers is sadder than "champion swinger" or not.

Lex's coward heart had been well established previously: given the choice of taking Superman with him in a blaze of glory or cowering away, yeah, he'd cower away. A more modern story, Luthor might have rode Superman to the center of the earth, laughing like the end of Dr. Strangelove...