Theories and such

Films and quirk singularity theory

We saw how AFO killed Nana - by causing an explosion as big as the island itself. It was shown in the film. So you could say something along the line "it's not canon" or something. You do you.
Anyway, we have seen that AFO was fine, while Nana - clearly exhausted and maybe injured a little. The only thing that AFO did - lift up a finger and charge the energy. From this moment forward, thanks to quirk singularity theory, his power grew stronger with each year.
Lets say that when he killed Nana - he was at the level of low or middle island (at least), and a lot of time has passed since than. Thanks to quirk singularity theory and time - he got to big or large island (highball? For an idea it means make something seem bigger than it is, I guess? But highball would be a country - continent level). But being able to destroy or attack at the scale of middle islands doesn't mean that he was as durable as the island. Okay, we saw that he was able in his weakened state take a city buster that was accompanied with a tornado just fine, but it can't exactly say how durable he is, or in that matter how durable he was in his prime. Seeing that All might did put a scar on this man, it would mean that it would at least be by attack at the level of... Let's say at least low island buster? Though idk, maybe he could use something a lot deadlier. But, seeing that he did put a scar by an attack of that scale, doesn't that mean that he could spam THE UNITED STATES OF SMASH in his prime? I'll say, this attack would also be stronger than a city buster... So All might in his prime could spam an attack that was at the scale of city buster+ (can't say at what scale this attack would be, but it would be higher than a city buster attack... Don't forget he can spam it seemingly)