Literally anyone could beat a guy who's been in a coma for two years… except they can't, because that would be an interesting story idea. Like, Kirito realizes that he's nowhere near as powerful in the real world as he is in the game world, and has to face new obstac- NOPE, instead we get cousin incest. Thanks Reki Kawahara.

Perry..? Sure, but without even using his agent powers, just his platypus skills.

L..? Yes. Without a Death Note.

Marvin..? Sure, by using his ray gun. By throwing it, not firing it.

Sokka..? Yes, by telling him some jokes that Kirito's character is not complex enough to understand.

Wendy..? Bitch, her gaze alone is enough.

Marco..? Yes. He literally fights stronger opponents on a daily basis.

Nichijou..? I heard there is nothing that cute anime girls cannot do these days.

And please, forget Markiplier: Tiny Box Tim alone would suffice for the job.