No hero is truly great without a nemesis who challenges them. Thankfully, My Hero Academia follows that rule to perfection. While the anime focuses on Izuku Midoriya’s journey to becoming a hero, its most iconic figure remains Izuku’s mentor, All Might. And All Might’s deadliest enemy is the terrifying All for One – a criminal mastermind whose intelligence and power make a deadly combination.
As much as All Might influences Izuku’s life, All for One has a huge effect on the world of My Hero Academia as a whole. His web of power spreads throughout the known history of the MHA universe, branding the lives of everyone who knows him.
This article contains some manga spoilers.
10 He Is A Force To Be Feared During The Dawn Of Quirks
All for One is born at a time before Quirks even existed. He and his brother, Yochi live through the societal upheaval that takes place during the dawn of Quirks. It's at this time that the villain manifests his powerful ability—the Quirk All for One—and uses it to take advantage of the chaos, making himself a force to be feared. He's shown taking Quirks from those who don't want them and giving them to another person who does.
In this way, he accumulates many Quirks of his own, but also a massive following as he practically becomes the ruler of Japan. Most of his activities seem to have taken place in the shadows, but he's still remembered as terrifying, even centuries after the supposed end of his reign.
9 He May Have Contributed To The Formation Of Hero Society
In My Hero Academia, society revolves around the usage of Quirks, and those without these abilities are deemed abnormal – practically subhuman. But during the dawn of Quirks, the situation was more or less the reverse. People with Quirks were seen as those who didn’t belong, and superpowered criminals who took advantage of their abilities didn’t help matters. In order to combat this state of affairs, vigilantes appeared to fight the powerful new threats. With time, their role became official and turned into the profession of Pro Hero.
All for One may have had an effect on the course of these events. His influence on the criminal underworld—particularly in Japan—would have created the necessity for superpowered protectors. At first, his opponents might have been vigilantes. However, he may have actually contributed to hero society by virtue of being such a terrifying threat.
8 He Accidentally Creates One For All
All for One may have been a criminal mastermind, but even geniuses make mistakes. Thinking his brother Yoichi is Quirkless, All for One forcibly gives him a stockpile Quirk. Unbeknownst to him, Yoichi does have an ability – that to pass his Quirk onto someone else.
The two Quirks combine to create One for All. While it isn’t a big threat originally, the ability grows with time, and in All Might’s hands, it becomes a powerful weapon against All for One and a tool that shapes society.
7 He Hunts Down And Kills All The Users Of One For All
After realizing the extent of his mistake, All for One attempts to fix it. To this end, he constantly hunts down every user of One for All. His quest to destroy or perhaps reclaim the Quirk he originally created indirectly shapes the world through the deaths of the heroes who are his targets. However, at the same time, his sadism and determination to make the users of One for All suffer give the inheritors just enough time to cultivate the Quirk.
For example, it seems unlikely that he couldn’t have hunted down Toshinori Yagi after the death of Nana Shimura, at a time when he was far more vulnerable. Even in the United States, he wouldn’t have been beyond All for One’s reach. He chose not to – probably because he wanted to make All Might suffer and prolong his agony.
6 He Takes The Quirks Of Countless Victims
The inheritors of One for All aren’t the only victims of All for One. Always greedy, the criminal mastermind seeks out interesting Quirks for his collection and steals them, seeking to turn himself into a one-man army. In this, he succeeds, as the numerous Quirks he has in his arsenal make him an unstoppable force for someone other than a One for All user. Even if they survive, the people who encounter him are left Quirkless – their destinies forever altered.
Some theories suggest that All for One may be Izuku's father and he may have actually taken his Quirk too. If that is the case, he may have been planning to set Izuku on a path for villainy—only to end up with another One for All user ready to fight him.
5 His First Confrontation With All Might Leaves Them Both Badly Injured
All for One may have indirectly created the Symbol of Peace. However, perhaps unsurprisingly, this also leads to his destruction. All for One and All Might's first battle ends with major injuries for both characters. All for One is severely mutilated, loses his sight, and needs life support equipment to stay alive, whereas All Might loses half his respiratory organs, as well as his stomach. The injury is so severe he never recovers. By the time the anime begins, he can only spend a few hours in his muscle form, and he knows that his time as a hero is coming to an end.
4 His Second Battle With All Might Leads To The Fall Of The Symbol Of Peace
Years after their first confrontation, All for One and All Might meet again during the Kamino Incident. After Katsuki Bakugou’s kidnapping from U.A.’s training camp, the Pro Heroes come to the captive student’s rescue, only to run into a threat they're unable to handle. It's up to All Might to defeat the powerful criminal mastermind.
However, All Might eventually reaches his limit, and under everyone’s horrified eyes, the secret of his skeletal form is revealed. With a superhuman effort, All Might still manages to defeat All for One, but it's his last battle and he's forced to retire.
3 He Provides Support For The Mad Genius Kyudai Garaki
All for One isn’t just dangerous for the enemies he makes, but also because of his allies. His followers are incredibly devoted to him, and he often finds recruits with great potential who are, for whatever reason, in dire straits. One such example is Doctor Kyudai Garaki.
The first proponent of the Quirk Singularity theory, Garaki is rejected by his peers for his ideas. All for One offers him his patronage, and it is through him that Garaki begins his nomu project. The creation of the nomu alone is a monstrosity that changes countless destinies. One notable example is heroics student Oboro Shirakumo, who's turned into the nomu Kurogiri.
2 He Grooms Tenko Shimura Into Becoming A Villain
All for One’s desire to see All Might suffer may have blown up in his proverbial face. However, on one notable instance, it pays off better than he himself may have anticipated. Tenko, the grandson of All Might’s mentor, Nana Shimura, is abused by his father Kotaro for his love of heroes. His Quirk Decay manifests violently, and he kills his whole family. In the aftermath, Tenko is taken in by All for One and groomed to become Tomura Shigaraki.
A popular fan theory suggests that All for One’s manipulations of Tenko may run deeper than what's immediately obvious. As Decay manifested at the age of five, Tenko could have been Quirkless and unknowingly gotten Decay from All for One. It certainly seems like something the villain would do. He may have even found it poetic considering his history with One for All.
1 He Takes Over Shigaraki’s Body To Become A Worldwide Threat
All for One may have turned Tenko Shimura into a villain to hurt All Might, but his later injury makes him important in a different way. The sinister villain instructs Doctor Garaki to pass All for One onto Shigaraki, having only kept a copy of the Quirk for himself during the battle with All Might. In the process, All for One also takes over Shigaraki’s body.
The process seems to blend the consciousness of the two characters, although it's (as of yet) unclear what the result will be. Either way, even in his current state, All for One has proven to be even more dangerous than before. Using Shigaraki’s body, he's already managed to kill Pro Hero Star and Stripe, and while the confrontation doesn't leave him unscathed, he definitely remains a worldwide threat.