This article is about the Quirk. For the Quirk's user, see All For One
All For One allows the user to steal the Quirks of other people, and wield those stolen powers as their own, or to transfer them to someone else.
The process of giving and taking away Quirks is done through touch. People who have their Quirks stolen become Quirkless, and lose any abnormal features if the powers happen to be Mutant-types. When Quirks are stolen, the victim becomes disoriented and immobile for a short time. Meanwhile, Quirkless people who receive a Quirk through All For One become capable of manifesting all of its attributes.
All For One can be used to combine several Quirks in order to create devastating techniques, which would normally not be possible with the usage of only one Quirk.
All For One's user hints that his wish is for Tomura Shigaraki to inherit his Quirk, implying that transferring All For One itself to another person is possible. This was revealed to have been already done by All For One some time ago, who had it extracted from his body to be passed on to Tomura while retaining a copied version of his original Quirk. It has been shown that the recipient of the All For One Quirk itself can access the Quirks that the previous user possessed due to the said powers becoming applications of All For One, rather than extra Quirks.
There are some limitations to the Quirk. Not all recipients of a Quirk from All For One are able to handle the strain of gaining them. Subsequently, they may become mindless dolls, who are not able to speak or think for themselves. Due to the chances of receiving a Quirk with and/or without drawbacks being at random, there are factors that can determine whether or not a person's body can withstand the Quirk-bestowal process. One of those potential factors is being Quirk-empowered prior to receiving a Quirk from All For One. Neither All For One's brother or Wolfram were put into a mindless state upon being endowed with a Quirk by All For One, most likely due to already being in possession of their own respective Quirks.
The effectiveness of the Quirks that are stolen by All For One depends on his own abilities. He stated that he did not want to steal Best Jeanist's Fiber Master, as it required too much training and experience to truly master, and implies that he prefers to steal Quirks with straightforward abilities.
All For One is incapable of stealing One For All from its wielder, as that Quirk can only be passed on if the present wielder wills it. Thus, wielders of One For All can act as a natural counter of sorts against All For One's ability to steal other Quirks. However, he was able to overcome this limitation in the past against previous wielders of One For All, due to the sheer number of Quirks he possessed. Furthermore, Kyudai Garaki performed various experiments on the body of Tomura Shigaraki so that the latter can be capable of stealing One For All, a feat All For One himself couldn't accomplish.
It's been discussed by Kyudai that, over time, the large number of accumulated Quirks within All For One was becoming dangerous to the user himself. While it seemed that All For One could allow the user to safely control any number of Quirks, there is a limit to how much the user can control without it adversely affecting them, like the Nomu. Garaki went on to state that if the "memory" (the amount of power of a Quirk) exceeds the hardware (the body of the Quirk user) then it will cause serious problems. This is somewhat similar to One for All, which requires rigorous physical training for the user to use to its fullest extent. This drawback was displayed during the Paranormal Liberation War Arc, when Tomura's body began to suddenly tear apart despite having Super Regeneration, which activated shortly afterwards. Tomura was intended to awaken with his newly enhanced body within 4 months, but was forced to out of stasis early due to Mirko shattering his capsule, leaving him at 75% of his intended strength. Due to this premature emergence and insufficient power, Tomura's body couldn’t keep up with the power of the All For One Quirk and the multiple Quirks stored inside it.
With Nine's variation of the Quirk, he was only able to steal up to 8 other Quirks. In his attempt to steal One For All from Izuku Midoriya, Nine was unable to do so, which he believed was due to his storage limit. He was most likely unable to because of One For All's unique properties. It's unknown if Nine's variation allowed him to transfer Quirks. In addition, due to the power of All for One, it put further strain on his body and caused the cellular degeneration from his Weather Manipulation Quirk to worsen. This drawback is the reason why Nine attempted to steal the Cell Activation Quirk of Katsuma Shimano so that he can rejuvenate his lost cells and continue using his various Quirks without limit.
The man who wields All For One once used his Quirk to dominate Japanese society over a century ago, using his Quirk to take away unwanted Quirks and give them to those who needed them, in exchange for favors. Eventually, All For One's user would amass a large following of loyal subordinates that carried out every single one of his wishes.
Later, this man would use All For One to empower genetically-engineered creatures known as "Nomu" in order to assist Tomura and the League of Villains with the achievement of their goals. Even after his arrest, however, Nomus with access to various Quirks are still being produced, and his role in this scheme, assuming he has any, is not yet known at the moment. The Nomus' creator, Kyudai Garaki, explained that artificially transplanting Quirks, most of which he was able to replicate, into a person's body requires complex surgery and takes at least 3 months to fully integrate into the chassis, but it's more difficult without All For One. This vindication postulates that All For One's ability to transfer Quirks onto people made the Nomu production process much easier.
For combat, All For One's user prefers to combine many of the Quirks he has collected throughout his life in order to maximize their power and effectiveness, often to truly catastrophic levels. Since this man has no qualms with killing, he doesn't hold back in fights, and will even target defenseless people, using them as a distraction to his advantage.
It's been suggested by All Might that All For One was used to obtain a Quirk that grants agelessness, explaining how its user is still alive to this day. This would later be confirmed by Kyudai Garaki who replicated his own Life Force Quirk and gave a copy to All For One.
At some point prior to the Kamino Incident, All For One had his Quirk duplicated, keeping the copied version for himself while the original was preserved until it was finally transferred to Tomura. It is unknown how powerful the duplicated version is in comparison to his original.
Nine donated his body to Kyudai Garaki of the League of Villains for experimentation so that he can become more powerful. During the process, Nine was implanted with DNA of All For One, and since his body was compatible with the latter's Quirk factor, he obtained the same power to steal Quirks from other people. However, his variant was much weaker compared to the original user, as Nine was only capable of stealing 8 other Quirks, and it's unclear whether he was capable of giving Quirks to others.
Foreseeing his defeat at the hands of All Might, All For One had his Quirk duplicated, keeping the duplicate for himself while his ally, Kyudai Garaki, preserved the original with the goal of having it transferred to his disciple Tomura Shigaraki. Kyudai would then perform a long and complex operation to transfer All For One to Tomura. After the operation was complete, Tomura was not only capable of wielding his master's power, but also had access to all of the Quirks All For One himself possessed.
- One For All's name is an inversion of All For One, showing the differing philosophies between their wielders. The former emphasizes one using their power for the betterment of others while the latter is meant to selfishly hoard power for one's own sake.
- The names of both One For All and All For One are in reference to the phrase "One for all, all for one", a motto commonly associated with the titular characters of the novel The Three Musketeers by Alexandre Dumas.
- One For All, All For One, and Life Force are the oldest known Quirks in the series.