All For One was arguably the strongest antagonist of the My Hero Academia universe and the former leader of the League of Villains. Although technically making his debut at the beginning of the series, he was best known for the fight in Kamino Ward in the middle of Season 3.
There are many factors surrounding the character that render him not only the scariest individual of his own series, but also the most intimidating anime villain alive. By identifying them, we can better appreciate the adversity that the professional heroes of Japan were forced to overcome.
10 All For One Can Give Quirks To Whomever He Wants
All For One was able to distribute Quirks to whomever he wanted, allowing him to embolden the powerless and create a semblance of "equality" in an uncertain hero society.
It was a fantastic tool for procuring the allegiance of others, as proven when he took the Quirk of a man who didn't want it and gave them to someone who did. Both recipients of his actions freely pledged their loyalty to him for the way he changed their lives.
9 All For One Can Steal Quirks Permanently & Stockpile As Many As He Likes
After touching an individual, All For One can permanently separate them from their Quirk. The only way for them to retrieve it is if he returns it willingly, as not even his death will release his ill-gotten powers.
All For One used this tactic against Ragdoll in order to procure her "Search" ability. Although All Might demanded its restoration during his trip to Tartarus, it would require the prison to disable its defense mechanisms in order for the villain to give her powers back. Unfortunately, this was too significant of a risk for the Symbol of Peace to take.
8 All For One Managed To Avoid The Authorities For Years
Ever since his first defeat by All Might, All For One was forced to the fringes of society. However, he still managed to fake his own death, thereby allowing him to run the League of Villains from the shadows and without suspicion.
When he finally came out of hiding to fight All Might at the battle of Kamino, even Japan's most hardened professional heroes were stunned and horrified. Should Shigaraki not have been so reckless, All For One could have continued to evade capture altogether.
7 All For One Dealt All Might An Injury He Would Never Recover From
While All Might managed to defeat All For One in an encounter before the series began, the hero did not emerge unscathed. He was dealt a massive blow to the side of his chest that would continue to burden him for the rest of his life.
It limited how much time All Might could use his Quirk. With each passing day, the maximum threshold he could harness One For All became scarcer, until he was finally forced to find a successor.
6 All For One Developed A Formidable Successor To Take His Place
After the injuries he incurred from All Might, All For One realized that he'd need a successor to ensure the future of villainy. He chose Tomura Shigaraki for two reasons; not only was he forlorn and therefore pliable to the man's influence, but he was also the grandson of Nana Shimura.
When Shigaraki's origins were revealed to All Might during the battle at Kamino, he was immediately demoralized and almost lost the will to fight on.
5 All For One Defeated Best Jeanist Instantly At Kamino
Best Jeanist was the first to confront All For One after his return to society. He used threads in order to bind the villain by his suit and attempt to make him vulnerable to attack.
Not only was All For One able to escape with little effort, but he also defeated Best Jeanist with a blow so devastating that he was forced to take a prolonged hiatus from hero work. Considering that the fabric hero was the third strongest pro at the time, such a feat illustrated how unrivaled All For One was.
4 All For One Was The Early Mastermind Behind The League's Actions
Before his arrest, All For One was responsible for the League's actions against Japanese society. This included the first attack on U.A. (which put the young students in danger and significantly reduced All Might's ability to use his Quirk), as well as a subsequent Nomu crisis.
Considering that he was able to rally a large number of villains to do his bidding in a short amount of time, All For One has proven formidable organizational and leadership skills.
3 All For One Publicly Humiliated All Might
Despite his loss, All For One made a complete mockery of All Might during the battle at Kamino. Not only did he trick him into punching Gran Torino, he also revealed the truth about his desiccated body on national television.
Further, the discovery of Shigaraki's origins was nearly enough to break the Symbol of Peace. Even after All For One's narrow defeat, All Might almost completely lost his ability to use One For All. Now, he can only harness his muscle form for a few short seconds for cosmetic purposes only.
2 All For One Murdered Nana Shimura
All For One was responsible for the death of Nana Shimura, All Might's former mentor and the previous user of the One For All Quirk. This made his interest to defeat him personal and further established the villain's reputation as a credible threat.
With the tragic and accidental death of Shigaraki's parents, it also meant that there would be no grandmother to look out for him. While All For One was more than happy to "adopt" his successor, it would likely have been better for all parties involved if he didn't.
1 All For One Is Still Alive & Still Has Access To His Powers
The most jarring part of All For One's legacy is that it is inconclusive. At the current point of the anime, he is still alive and fully capable of using his abilities, whereas All Might cannot.
Tartarus is so concerned with containing him that even the mere thought of accessing a Quirk would trigger a bullet through the criminal kingpin's head. The villain is content to wait; with the tools he has provided Shigaraki, he is confident that the future of the League will be secure without his guiding hand.