All Might is one of the strongest characters to have ever lived in My Hero Academia. Starting his journey as a Quirkless boy, Yagi Toshinori was bestowed with the powers of the One For All and he became the eighth user of this Quirk. His skill kept growing to a point where he became a phenomenon and a legend, renowned as the Symbol of Peace in Japan.
As the Number One Hero, he was strong enough to face All For One and even defeat him in battle on more than one occasion. Since All Might has reigned supreme as the greatest Hero for quite a long time in the story, he has had several forms or costumes over the course of time. While some of them are rather recent, others have existed decades ago.
5 Final War All Might
All Might decided to join the Final War as the battle started getting closer to its climax recently in My Hero Academia. Towards the end, he took it upon himself to stop All For One, who was beyond his prime level at this point. Although he is Quirkless, he still has enough belief in his abilities and that is certainly incredible to see.
All Might is not unarmed, however. He carries with him a suitcase which most likely has a battle armor for him. It is unknown how strong this battle armor is and, for that reason, it cannot be ranked properly. That said, since he does not have the One For All, this form of All Might is likely going to be the weakest that the fans will ever see in the story. However, if he does manage to defeat All For One, who is actually beyond his prime at this point, then this form of All Might will actually become the strongest.
4 Young Age All Might
Young Age All Might is him at his youngest as a Pro Hero. Fans got a glimpse of this form of his during the Two Heroes movie where David Shield ended up revealing that he was the one responsible for designing all four of All Might's costumes throughout the ages. Young Age All Might is one who is far from his prime and still growing in terms of power.
At this point, All Might was still in America and did his job there pretty well. Despite not being at the pinnacle of his strength, he was still incredibly powerful and that is certainly evident from the small glimpses that the fans got of him in combat. While still in his youthful exuberance, All Might did not have the experience that he has today.
3 Bronze Age All Might
After the Young Age All Might came the Bronze age ll Might and, sadly, fans have not seen much of him in this form. However, it goes without saying that Bronze Age All Might was likely much stronger than Young Age All Might. This form of him would have acquired a lot more experience and, also mastered the powers of the One For All to a much greater degree.
His fighting prowess would have been incredible and it is possible that he returned to Japan at this point and started working towards his goal of becoming the Number One Hero. Still, Bronze Age All Might was still the very beginning of his legend and not him at his peak. That said, Villains all over the world would absolutely hate the idea of facing him in battle even when he was in his Bronze Age.
2 Silver Age All Might
All Might in his Silver Age was likely much more experienced and had established himself as a great hero in Japan already. Fans have seen him don this costume during the Training Exercise arc where he fought against Bakugo and Deku. This red costume with a flowing cape from the back made All Might look much more like a superhero and flashier than his final outfit.
In terms of power, however, he was still not at his pinnacle as this is not a costume he wore during the era where he established himself as the Symbol of Peace. Judging by that, it appears that during his Silver Age, All Might might still have not conquered crime in Japan and become the pillar that he ended up becoming later on.
1 Golden Age All Might
Finally, the most well-known form of All Might that the fans are used to seeing is the Golden Age All Might. In this form, All Might wears a blue costume and golden that was specially designed by David Shield in order to allow him to function at his very best.
In the Golden Age, All Might became the Symbol of Peace and established an era of peace in Japan. He became the pillar that the Hero Society needed and, at the same time, he also crushed All For One, the greatest Villain in the entire story.
In doing so, he also received a significant injury and this weakened him. Despite that, All Might continued being the Symbol of Peace and later on, fought All For One once again. In this clash, in Kamino, he managed to power through once again and defeated All For One, sending him to Tartarus in the process. All Might's golden age came to an end on that day and, since then, he stopped being a Hero, that is, until the Final War, where he once again steps into battle for one last time.