In a realistic sense where they both go all out Superman could **** Batman in milliseconds if he wanted. Looking at it from a logical conclusion there is just no other way to see it. He could nuke Batman from space with heat vision if he felt like it, but really there is no real way to answer the question as both go to ridiculous lengths to not **** people, and Superman doesn't even like hurting anybody more than the least amount possible to get the job done.
not my area of expertise, but let me play along.
what is the area of effect of kryptonite? What's to stop superman from hovering out of that range and using his laser beam eyes to turn batman into a pile of smoldering flesh and melted latex?
The krypontite's radiation saps Sup's strength and powers, rendering him a mere mortal, and would eventually **** him, and while he could use his laser vision to zap Batman from space, Sup is usually too nice to fight like that, and Batman knows about the laser vision and would be prepared for it in some way, I mean he does have a global, very diversified, multi-billion(or is it trillion now?)-dollar business to back him up. Meaning Batman could show up with a kryptonite-powered laser of his own to return fire. Or, if Batman wanted to be nice about it, he could also lure Superman into a room artificially lit like by a red star to make Superman normal.
If batman has kyptonite then he wins if not it's no contest.
Forget nice, this is who would win in a theoretical. Ok, superman flies the planet earth into the sun thus ******* batman. That's your nuclear option, literally.
Then he goes and lives on mars.
The end.
I think a better question is who would win -- Batman vs Spiderman?
I'm just going to leave this here.