Think it was Nienami cutting a boat.
That was an AP feat, but it was done through Contradictory Conjunction, making it inapplicable for an AP rating or scaling, and it was done in one of the later arcs; it doesn't backscale.
I'm seeing now the profiles of the verse but I didn't saw a calc nor a scan which can back up such tier, and I found just a 9-B and a 9-A calc about the AP. Can someone explain?
The source of the AP is explained on the profile; it's Medaka dragging part of the school around a few dozen chapters in. However, there's a lot of issues I found with this which I planned to eventually tackle in a CRT, but I never got around to it.
That feat and a few others were calced
here. The only legitimate method (imo, I'm willing to argue this) puts that feat at 9-B+. But some other feats were calced, which present their own issues for scaling.
Another calc revolves around
this scan. While "It's actually a good thing I didn't blow off this entire wing" can be interpreted as "This would have fragged the entire wing if Medaka hadn't stopped it", I don't think that's a very strong interpretation, maybe only good for a possibly at most, and with Blahblah's reasoning, would only put Medaka at High 8-C.
The last calc has Iihiko destroying a hospital. This occurs right at the end of the manga, after Iihiko moves to a more powerful body. There's only 3 characters who fought him after that, two of which used hax to boost themselves to his level, and it still only reaches High 8-C.
While I'd still like to do this revision one day, I have about 15 verses I'm planning on revising, as well as 3 currently ongoing revisions. So I won't be getting to it any time soon.