Weakened and cuffed All Might warm up air punch could destroy city buildings.
Now imagine Prime Might vs Prime AFO ( after that fight Might got weakened ).
If Prime AFO and Prime Might weren't High Dragons ( using OPM scale ) then I'm done.
This is obviously a huge benefit of the doubt since we can only gauge AFO's power over "potential" Prime Might level and that scene from All Might special but I think it's not far fetched to give AFO the W.