Well, I know most feats in SpongeBob tend to get downgraded because of their supposed size, but the sizes of characters in SpongeBob actually vary ALOT. Sometimes SpongeBob is the same size as humans and meta-humans, other times, he's less than the size of a human foot.
There's also that MFTL feat with Patrick, and in Battle For Bikini Bottom, SpongeBob fought many building sized robots.
And we can't forget the cherry pie bombs which are based on an actual nuke (and even uses actual footage from it for the explosions) that's name sounds suspiciously like Bikini Bottom. If I could remember the name for the life of me, I could figure out how powerful it is and scale that to SpongeBob's durability considering he and Squidward most likely tanked it.(Well, SpongeBob anyway. Squidward was obviously hurt.)
I heard about a mountain level feat with Sandy. Could you link me it or tell me what episode it's in?