Ok, so I was noticing that at 18th a Barbarian can substitute their STR score for any STR based check roll, and at 20th they get +4Str and Con, which means they can have(almost certainly will have) at least a 20 STR and more likely a 24 STR on top of that. If the barbarian also has athletics, and what self respecting Barbarian wouldn't, even if you cap the roll at 20 instead of the actual STR score of 24, that would mean a DC33(auto roll of 20 +7 for STR +6 for Prof) is their new minimum roll. So they can always perform insane herculean feats of Strength right? At first this seems overpowered but then I remembered 20th Level is up there with the greatest heroes of legend(Sampson, Hercules, Beowulf), so not totally out of line if a DM is going there anyways.