Which ultra-durable Marvel character would beat the other?
I don't think either could hurt the other. MM definitely can't hurt Kimura if X can't cut her under any circumstances and giant buildings falling on her don't do anything. And Kimura isn't stronger than Peter, and MM mostly no-sells Pete's shots. Kimura might have access to gear that can cut him, but that would take prep. In the end, Kimura is a MUCH better fighter, being good enough to beat X-23 in HtH and not get hit a couple of times (not that the hits would matter), so she might win by just pounding on MM effectively forever, or she might be able to force a 10-count somehow.