Mirko seems to have greater AP than 20% deku
She was easily cutting through flesh with her kicks whereas Deku's 20% failed to sever Overhaul's arms, something Mirko likely would have been able to do given her feats in 260
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Its due to this that I think Deku needs to have mastered more than 20% over the timeskip. With Ujiko backed to the wall, its only a matter of time before the high end noumu are released. And we know that these guys all likely posses some form of super regeneration.
Due to this, if Deku is going to be able to defeat a high end, he'll need to be capable of throwing punches & kicks that can blast threw flesh. Something that Redestro, Mirko, and All might have shown.
One of the ways that Deku could possibly reach OFA 50% or even higher would be to channel the power of OFA equally between his body and his other quirks. For example, Deku would coat himself in blackwhip in order to enhance his strength. He would channel 20% of OFA through his actual body, 20% through black whip, and 10% through float, allowing him to reach 50%. IDK if OFA really works this way but it seems like it does.
Otherwise perhaps coating himself in blackwhip like Venom would be enough to enhance his physical strength to get near 50. In any case, I think Deku should be near 50 and have both blackwhip and float mastered. I think this should be the minimum given that All Might had 100% mastered by the time Nana died