In My Hero Academia, we all know that Izuku Midoriya, otherwise known as Deku, inherited the One For All Quirk from All Might, as this Quirk allowed him to gain a Quirk of his own despite being born without one. Of course, Deku is still quite young and is yet to fully master the power of One For All, which requires someone to be very strong to wield it. We also know that All Might was once the greatest hero in history and was the best at using One For All. So, in a fight between Deku and All Might, who would win?
All Might is likely to win a fight against Deku despite the fact that Midoriya is now stronger than ever in the Final War arc. That’s because All Might was able to use the full power of the stockpiling ability of One For All even though he doesn’t have Deku’s access to the Quirks of the former holders of One For All.
The fact that Deku was the only one to gain access to all of the Quirks of the previous holders of One For All is the reason why he is so unique compared to all of the other users of this powerful Quirk. Of course, while he should be stronger than All Might ever was, his body and experience are yet to keep up. So, with that said, let’s look at this hypothetical battle in greater detail.
After inheriting One For All from All Might, Izuku Midoriya became Deku and is now the ninth user of this powerful Quirk despite the fact that he wasn’t born with a Quirk. However, because of his weak body, he didn’t have the capability to wield One For All in its full power, even in the Final War arc. In fact, in the manga, Deku can only access 45% of its power without getting hurt, but he only uses 45% in the last second and in conjunction with Blackwhip and Fa Jin to create a Faux 100% One For All attack without getting hurt.
Throughout his time as the user of One For All, All Might almost never had any problems with it, as he even told Deku that he could use the Quirk almost immediately after inheriting it. As such, during his prime, he could use the full power of One For All without suffering any of the drawbacks and injuries that Deku suffers whenever he uses the full power of the Quirk. And All Might was so strong that he was basically unstoppable during his prime, as only a prime All For One could actually match him.
Theoretically, Deku should be stronger than All Might because One For All is a stockpiling Quirk that strengthens whenever it gets passed on from one user to another. But the fact that he can’t use One For All in its full power without getting hurt is the reason why All Might is still stronger.
Deku 0, All Might 1
When using One For All, Deku is very durable as his body strengthens to a point where it can take powerful attacks without a building-sized explosion from Bakugo, even when using only 5% of the Quirk’s power. At 30%, he is capable of taking attacks from an enhanced Tomura Shigaraki. Then, when he’s at 100%, he becomes almost invulnerable but ends up suffering from the drawback of the Quirk’s power, and that’s why using 100% of One For All is a double-edged sword for Deku.
All Might, in his muscular form, is almost always at 100% of One For All, and that means that his durability is at a level that is beyond imagination. In fact, he was able to withstand attacks from a powerful Nomu without showing any signs of damage at all. He even took on a blast from Bakugo at point-blank range without getting hurt. And the only character to ever hurt him was All For One, who had to use all of the Quirks he had in his arsenal to damage All Might and seriously injure him.
Again, Deku should be more durable than All Might, in theory, if he masters One For All. But the fact that he is yet to master the Quirk is what makes All Might much more durable than him. And All Might simply had a gifted body that allowed him to master One For All faster than the others could.
Deku 0, All Might 2
As mentioned, Deku inherited One For All from All Might as he was born Quirkless. But, over time, he ended up discovering that he could use the Quirks of the other users of One For All as well because it was during his time that the One For All Quirk matured and evolved. As such, Deku has six other Quirks on top of One For All, and these are Gearshift, Fa Jin, Danger Sense, Blackwhip, Smokescreen, and Float. Using Gearshift and Fa Jin allows Deku to move faster while using Float allows him to fly.
All Might was born Quirkless but inherited One For All from Nana Shimura, the seventh user of One For All. When he inherited One For All, he didn’t take too long to master this Quirk because he was born with a gifted body that could withstand the power of One For All. On top of that, the fact that he was born Quirkless allowed him to use One For All without any drawbacks to his lifespan, and that is the reason why he is still the best to ever use the Quirk.
It might be true that All Might’s mastery over One For All is light years ahead of Deku’s own mastery of this Quirk, but the fact is that Deku is the only one out of all of the nine holders of One For All to gain access to the Quirks of the other users. This gives him an edge in this department.
Deku 1, All Might 2
Deku, being as young as he is, doesn’t have a lot of feats. However, he has already achieved incredible feats as the holder of One For All, as he was able to defeat a powerful villain named Overhaul by using the full power of One For All during the time when Eri was using her Quirk to reset/heal Deku’s body in that fight. Deku also speed-blitzed an injured Tomura Shigaraki during the events of the Paranormal Liberation War arc. And in the Tartarus Escapees Arc, Deku defeated a powerful villain named Lady Nagant.
We don’t know all of the other feats that All Might had when he was still younger, but we do know for a fact that he was the only hero that could stand up to the supervillain named All For One, who has the ability to steal, use, and give Quirks. The fact that All For One was basically untouchable to the other heroes but was afraid of All Might allows us to understand just how strong All Might was during his prime. And it was during his prime years that he injured All For One to such an extent that he forced the villain to find a suitable successor to his power.
It might be true that Deku has already defeated a bunch of powerful villains during his run as the holder of One For All. But the fact is that All Might, without the use of the Quirks of the other users of One For All, defeated All For One in his prime. That says a lot about how strong he is.
Deku 1, All Might 3
Deku has only been the user of One For All for about a year since he started attending UA High School. While he has fought a lot of heroes and villains alike during his run as the user of this powerful Quirk, he hasn’t had the same kind of experiences that pro heroes have had. And that’s because Deku is still just a young hero that’s on the rise.
All Might’s experience is vast because he was the top hero in the world during his prime. That means that he was the one who was sent to missions involving some of the most powerful villains the world has ever seen. And the fact that he was already around 48 years old when he gave One For All to Midoriya means that he was active as a hero for about three decades.
Of course, the fact that All Might is so much older than Deku is the reason why he has more experience than the younger hero. Nevertheless, Deku has already had a lot of experience fighting villains in what has been an eventful first year for him at UA High School.
Deku 1, All Might 4
Deku vs. All Might: Who Wins?
In theory, Deku was supposed to be stronger than All Might because he could use all of the Quirks of the other users. But the fact is that he is yet to master the full power of One For All, which All Might was able to use like it was second nature to him. On top of that, All Might’s experience and feats speak for themselves. As such, while Deku should surpass him in the near future, Prime All Might is still the pinnacle of the One For All Quirk.