Of all the quirks in My Hero Academia, One for All is one of the most unique and most mysterious. It helped All Might become the symbol of peace that led Japan into the age of heroes, and now it's been passed down to Izuku Midoriya, a young boy without powers who had the heart of a hero.
But Midoriya is known to be the ninth user of this ability, so many people have wielded it before him. Just what is known about the previous users of One for All, and what did they add to that power? The true history of One for All has been revealed throughout the course of the My Hero Academia manga, from its early origins all the way up to the present day. Here is an explanation of every person before All Might who has wielded the One for All quirk.
Yoichi Shigaraki
Yoichi Shigaraki was the First User of One for All, and brother of All for One. Born in the era where quirks first appeared, he originally seemed to be quirkless, whereas his brother had the ability to steal quirks and bestow them onto others. While All for One sought power, using his ability to make people indebted to him and become his loyal followers, Yoichi struggled to end his brother's selfish motives. He was rather sickly, however, and without a quirk, he could do little to stand in his brother's way.
Despite his faults, All for One did seem to possess a true love for his brother, which led him to grant Yoichi a power-stockpiling quirk. As it turned out, Yoichi wasn't quirkless after all, but rather possessed a quirk that could be passed from person to person, with no other signs. These abilities combined, creating the inheritable, power stockpiling quirk known as One for All. While Yoichi was never able to stop his brother, he established the tradition of passing One for All on, always with the goal of finally ending All for One's evil acts.
The Second User
Little is known about the Second User of One for All in the present chapters of the manga. Both the Second and Third have been reluctant to trust the overly idealistic Midoriya, so he has not been able to utilize their quirks, and unlike the other vestiges, they have not spoken to him directly. It's known that the Second User was part of a resistance group fighting against All for One, and that he and his team had intended to assassinate Yoichi as part of a plot to overthrow him. He carried with him some sort of gun-like gauntlets, which may have been related to his quirk. The Second User found Yoichi locked in a dark room and changed his mind, agreeing to work together. The sickly Yoichi passed the quirk on to him, and they used this new power to fight back. While the Second has begun to come around in his feelings towards Midoriya, the quirk he contributed remains unknown.
The Third User
The Third User of One for All is just as mysterious as the Second; it's known that the Second and Third fought side-by-side in the resistance movement, and that the Third was also present when Yoichi was found. He seems to have a similar perspective towards Midoriya as the Second as well. The Second passed One for All down to the Third in dire circumstances, although the exact details have yet to be shared. Yoichi's vestige was finally able to convince him to work with Midoriya as well, drawing a comparison between Midoriya's compassion towards Tomura and the Second and Third's compassion towards him. His quirk was first used in Midoriya's battle against Lady Nagant, where it was revealed to be based on the martial arts practice of "Fa Jin," an explosive release of power by coordinating the body's movements.
Hikage Shinomori
Hikage Shinomori was a pro hero and the Fourth User of One for All; his name contains the Kanji for "four," a trait shared by most previous users. His quirk, Danger Sense, allowed him and his successors to quickly react to dangerous situations, and also made him prefer solitude. While Danger Sense has some obvious benefits in combat, it wasn't the kind of offensive ability that was needed to battle All for One, who had continued to grow stronger. Shinomori decided to train One for All and grow its power instead of confronting All for One directly, which helped him to become the longest-lived One for All user besides All Might. His long lifespan also helped to identify the damage that handling multiple quirks can do to a person's body; as he aged, his body began to develop distinctive fractures, and he ended up passing away from "old age" at only 40 years old. This period of training was invaluable for stockpiling the power in One for All, and Shinomori made sure that his successors would be able to handle it.
Daigoro Banjo
The Fifth User, Daigoro Banjo, was also a registered professional hero under the name of Lariat. He was born with the quirk Blackwhip, which generates dark energy into a whip-like form and uses the wielder's emotions to maintain itself. It can be used to grapple, restrain, and move, making it fairly versatile. As a pro hero, Lariat went up against All for One directly, narrowly avoiding having his quirk stolen on more than one occasion. He was able to make use of the power, speed, and agility that One for All granted him in addition to Blackwhip, which aided him in becoming a top-tier hero. Banjo was also the first to reach out to Midoriya, explaining how to use Blackwhip when the power erupted from him unexpectedly, and warning him that the other quirks may soon materialize as well. Banjo had a larger than life personality, which even his vestige has managed to maintain.
En
The Sixth User, En, was Daigoro Banjo's protégé, and another pro hero, although little is known about his career. His quirk, Smokescreen, provides the ability to obscure one's location in a cloud of smoke. When Banjo was mortally wounded in battle against All for One, crushed beneath rubble, En found him and was able to receive the power of One for All via his blood. He seems to be much more of a quiet, brooding type than his predecessor, with a high-collar costume that often obscures his expression. En recognizes that most users of One for All just happened to be in the right place at the right time, rather than being chosen, so he can acknowledge the limitations of many of their quirks, claiming that Midoriya had "too much" respect for them in his fight with Muscular. En also battled All for One directly on several occasions, and managed to avoid having his quirk stolen at least twice as well.
Nana Shimura
Nana Shimura was the Seventh User of One for All, the only female user, and as a pro hero, All Might's former master. Her quirk, Float, allowed her to levitate and maneuver to a limited extent while in the air. Nana Shimura is the only previous user who is known to have married and had a family as well; the man currently known as "Tomura Shigaraki" was once her grandson, Tenko Shimura. She was present for En's death, and received the power of One for All from him via hair, like Midoriya. Nana trained All Might, who at the time had no quirk but a strong desire to become a symbol. She decided to take a chance by allowing the quirkless lad to inherit the power of One for All, revealing that it reached its true potential in the hands of the quirkless. While it's said she was a good mother, the hero life didn't allow for her to be there as much as she should have, and her eventual death at the hands of All for One left her son alone. She has arguably had the largest impact on her successors aside from the First, as All Might's philosophy of always smiling and looking in control was originally hers, continuing her legacy in the world of My Hero Academia.