Theories and such

The Kamino AFO and All might

All might and AFO.
Those two have a big impact on MHA. AFO - the man who wants to become a demon lord (Or just as powerful as he can be?) and All might - the man who put the hero society on his shoulders.
What exactly happened in their fight when they fought in their prime? It was stated that this fight happened five years prior canon. We know that AFO damaged All might - giving him a destroyed stomach and respiratory system, while All might - destroyed the face of this man, rendering him unable to live without a life supporting machine. But, was it really everything that happened to them? Probably yes, but wait, shouldn't that mean that All might also destroyed AFO's brain? Or at least in their Kamino fight (check the gif)? That is unknown.
What I know for sure - that this last attack of All might was likely a city buster. But, is it really that powerful if we compare it with Prime AFO and All might? Probably not. As we have seen, after this attack WEAKENED AFO (this dude didn't even had his original quirk for an idea) didn't die, heck, he even seemed almost unfazed by this and was talking. So, what exactly did prime All might do to put this scar upon AFO? Let's take into consideration that AFO was a lot more durable, plus from their fight 5 years has passed and AFO probably gave away some quirks that were not useful for him. Plus Nomu's. Meaning that he lost even more quirks. And even than, a city buster attack did seemingly nothing to him.