What does it take to hurt Superman (ASIDE from Kryptonite)?

He’s photosynthetic. Total darkness over a period of several days. Let his batteries run down.

Then again, I think Byrne had something about him being able to completely metabolize the food he eats. Maybe he could supplement his energy reserves with random organic matter. So, total darkness and nothing which he could use for chemical energy.

Yes, but how do you restrain him in the meantime? Seems to me that if you have the tech to confine him in one place, you have the tech to kill him outright, and doing so quickly is a better idea than dragging things out, thus giving him the opportunity to suss out a way to escape.

Luthor did a number on him with the powerstone back in Superman #17 (which volume I have safely stored in my vault.) He did it again in Action comics #47 (which sadly I lack a genuine copy of.)

Screw around with the memory crystals in his Fortress of Solitude so when he goes to talk to his mom, she’ll tell him that mixed marriages never work so he’ll get in the power removing chamber so he can sleep with Lois lane and then POW!

So…like this?

How about getting him to sleep in a closed room in Korea with an electric fan running?

Bet him that he can’t rip his own head off.

The Silver Surfer would have an extremely difficult time defeating Superman. The reason why is left as an exercise for the reader.

The Surfer would agonize and introspect until Superman just flies away?

The five point palm exploding heart technique.

Heck, as far as I can tell that’s what Miller has the big guy do in THE DARK KNIGHT RETURNS.

Restrain him? Snuff the Sun, and he won’t have the energy to escape the Solar System in time. In a week or so, he’s down to being merely a large muscular corn-fed farm boy. Look, do you want to keep the Sun going, or do you want Kal-El dead?

This begs the question. How did he get hired at the Daily Planet without a TB test? And why doesn’t somebody just collect Clark’s fingerprints and match them against Superman?

Does Superman leave fingerprints?

Yes, but he makes a super-speed pass with a handkerchief over every smooth surface he’s touched before he switches back to Clark.

Alternatively, from the invulnerability-as-a-forcefield writers: no, because he never actually touches anything directly while his invulnerability is in effect.

Note–gravity-based attacks have also been effective in the past.
Match Krypton’s old gravity, multiply by 20, and you can put him in a bad way.

Psionic abilities can and do work.

The extraterrestrial parasite Starro can control his mind.

Diseases from Krypton could be quite effective.

One skanky Kandorian hooker could put him on the ropes pretty quickly.

The Surfer loses fights he should win because he really dislikes fighting and has a hard time getting himself into the right headspace. Admittedly Superman is hardly a berserker himself (and spends most of his time dealing with natural disasters and so forth, not fistfights), so he’s more aggressive than the Surfer. The Silver Age Superman could probably defeat the Surfer. Their power levels were similar (though the Surfer has some extra abilities), but Kal is more aggressive than Norrin. Contrariwise, I think the post-Crisis Superman would lose (and has) lost against the Surfer.

I’m thinking now of times both of those have done really well in battle. They both shine against vastly numerical superior forces using technology, especially starships and robots; I can think of occasions in which each have destroyed entire alien armadas all by their lonesome. (I doubt Silver Age Supes would even call on the JLA for help against something like that.) With Supes and the Surfer you’re better off with single opponents who are clearly sentient beings, even if you have more powerful options available.

If you’ve got the juice to snuff out Sol, you’ve got the means to kill him by brute force.

He could simply absorb all of Superman’s solar energy

Actually, I was thinking more along the lines of it being difficult for the Surfer to defeat him, because a prerequisite to that would be for them to be in the same universe. Which has admittedly happened occasionally, but it’s rarer than it is for Squirrel Girl to defeat cosmic forces.