Let's start with an easy one: Ichiro Suzuki/Satou Pendragon from Death March to the Parallel World Rhapsody.
Dude is solidly planetary (as in one time he was flying around in space and picked up a planetoid to use as a sword against a Cthullu monster) and not only has resistance to basically everything Ainz can use but also has some kind of "you can't bypass my resistance" skill meaning GoALiD isn't going to work
He's also FTL, if the whole "flying around in space" thing didn't make that clear.
He's also the platonic ideal of "boring ass generic MC" in modern LN
Round 1: Medaka Kurokami. Likely weaker physically. But way faster from copying Hinokage's "theme song" ability, and has more than enough copied hax to fuck Ainz up.
Round 2: Shinrabanshoman. Dude can fuck with the concept of death to "lessen the value of life", rewind time, transmute the embodiment of despair into Soul Eater's sun, etc...
You know what? Fuck it, the hilarity of this is too much. Kai from Beyblade roasts his ass with Dranzer. Imagine Ainz' reaction to getting soloed by a spinning top.
If the Earthquake feat from Yujiro, and Oliva's strength fucking with satellites is useable and scalable to Baki, then yeah, you could argue Baki beats his bony ass.