- Law's puncture wille breaking Big Mom's bones, same puncture wille that didn't deal fatal damage to Blackbeard, who has no crazy durability and has pain and damage dealt to him amplified by the Yami Yami no Mi
- Big Mom feeling the need to use Haki to block a Kong Gun with basic Haki
- Big Mom falling off the plateau made everyone consider it the end of the Big Mom pirates, with her needing to be caught by Zeus
Noodle: "You need Bajrang or Blazing Bagua level of attacks beating Big Mom.
Apart from that, again, it's clear that Shanks is the new gen Roger. He even used Roger's exact same move.
Sure. Titles aren't permanent. With Shanks being such a prominent end game villain or character which Oda portrays in the best light possible, it is entirely possible for Shanks turning out to be stronger.