All For One

Sensei (先生) is the true leader and founder of the League of Villains and the main antagonist of the series.

Appearance
Sensei's face has a completely deformed head from above his upper lip he has a massive scar that also extended behind his neck, while also missing both his eyes and nose. He also has two tubes in his throat that allow him to breathe.

In flashbacks, he appears to be an ordinary looking man with short hair. However, his face is not seen.

Whenever Sensei appears outside, Sensei adorns a black ornate mask and a life-support system around his neck while wearing his suit.

In each appearance to date, he has always been seen wearing a suit.

Personality
Sensei has a sinister, twisted and methodical personality, being able to have multiple plans coordinate with one another simultaneously. According to All Might, Sensei is manipulative and exploits people; Sensei appears to also be a misanthropist as All Might noted that he laughs and scorns at humanity for their continuing hardships.

However, in contrast to his evil personality, it appears that Sensei does indeed care for Tomura; as he was livid that the Pro Heroes and Police Force were bothering Tomura when he was beginning to think and lead for himself. Sensei does not mind failure and instead encouraged Tomura to keep trying.

Despite Sensei's methodical mind, he has shown to also be quite impatient, as he wanted to get rid of the Pro Heroes and Police Force attacking the League of Villains as soon as possible. Sensei also appreciates strength when he sees it, as he praised Best Jeanist for his quick thinking.

History
The introduction of Quirks to the world led to a period of societal collapse and an age of upheaval. During this time, a man (who would become Sensei) with an overwhelmingly powerful Quirk called All For One, arose in Japan and decided to take advantage of the chaos. He stole many Quirks which gave him immense power and influence. Using his incredible might, the man gathered and unified dozens of people under his command. He then manipulated the people he gathered like pawns to further his plans and eventually became Japan's ruler. It's suggested that he ruled from the shadows, as most of his actions in the present day are only known as rumors on the internet.

Sensei's younger brother opposed his evil. For unclear reasons, Sensei used All For One to forcibly give his little brother a Quirk that could stockpile power. What no one knew at the time is that Sensei's younger brother already had a Quirk with only the ability to pass itself on to others. The two Quirks mutated, blended together and would later become known as One For All.

Sensei's younger brother was not strong enough to defeat him with his new Quirk, so he passed it on to the next generation in the hopes that one day One For All would be strong enough to defeat his older brother. It is suggested that Sensei would fight these successors.

Later on, Sensei killed All Might's predecessor Nana Shimura. All Might eventually fought and defeated Sensei, but received a debilitating wound in the process.

Incapacitated by his defeat, Sensei went into hiding as he attempted to heal from his injuries. He would later create the League of Villains (where he took on his "Sensei" identity) and appears to be grooming Tomura Shigaraki as his successor.

Unforeseen Simulation Joint Arc
Kurogiri warps himself and Tomura back to their hideout at the last second, allowing them to escape from being turned to dust. Tomura complains that his body hurts and all their subordinates were eliminated, Noumu was defeated and All Might is still alive, further complaining that everything went wrong. However, Sensei, speaking on the monitor says that nothing went wrong and that he was simply over optimistic. Sensei says that it is too late to mourn and that they should gather a new group hand picked for efficiency, saying that they should take all the time they need. Sensei says that Tomura is a symbol of importance and that next time he will show the world the horror of his existence.

Sports Festival Arc
A recuperating Tomura was seen watching the Obstacle Race with his computer and he sees that Izuku took first place. Later on, before the battle between Izuku and Shouto begins, Sensei tells Tomura to pay close attention to Izuku and Shouto's match as they might become obstacles for him in the future. Tomura responds by telling the Sensei to not make him laugh.

Field Training Arc
Sensei, using the monitor to speak through, orders Kurogiri to allow Stain and Tomura to continue talking, saying that Tomura's meeting with Stain (an experienced infamous villain) will stimulate Tomura's growth. Before he leaves for Hosu, Tomura asks Sensei to let him borrow some Noumus because he does not like the "Hero Killer" Stain and that destroying things he does not like seems alright. Sensei decides to give Tomura three Noumus, hoping that Tomura will make the opportunity a learning experience.

Sensei is surprised that the Hero Killer Stain was captured but is still happy that things are going as he has foreseen. He exclaims that Tomura's position is to supervise and unify the new villains who have come to join the League of Villains. The Sensei's doctor expresses doubt that Tomura can do his job and says that if Sensei stepped in things would be proceeding faster. Sensei asks the doctor to patch him up faster. Sensei says that he will let Tomura do all the hard work so that he may become his successor as Tomura was born to do so. Sensei tells All Might to rejoice in the "transient" peace while he still can.

Hideout Raid Arc
After Katsuki attacks Tomura, Tomura understands that mere words alone will convince Katsuki to join them and decides to ask for the "force" of his teacher, Sensei, to help him convince Katsuki. Sensei, who has been watching Tomura on his computer, commends his apprentice for his wise decision.

The League of Villains is apprehended by the Pro Heroes and Police Force. Sensei decides to take action himself. Sensei appears at the League of Villains' warehouse and apologizes to Tiger, explaining that Ragdoll is in a comatose state because he stole her Quirk, Search, which he found to be quite useful. Best Jeanist restrains Sensei with his Quirk and orders his fellow Pro Heroes to not let the villain do anything.

Before the Pro Heroes can act, the entire warehouse is completely destroyed and the surrounding area has suffered extensive damage as well. It is revealed that Sensei unleashed a blast wave that has seemingly killed the Pro Heroes, destroyed the warehouse, and dealt significant damage to the surrounding area in less than a second. Sensei is livid with the Pro Heroes for interfering with his apprentice, Tomura who has started thinking for himself as well as leading others by himself, and hopes they no longer bother him. Sensei decides to quickly resolve the mess created by the Pro Heroes.

Sensei uses a Quirk to produce black liquid at the League of Villains' hideout; the black liquid summons dozens of Noumus inside and outside the hideout, forcing the Pro Heroes and Police Force to confront the legions of Noumus. This black liquid also teleports Katsuki away.

Sensei sees that the Pro Heroes survived his attack. Sensei claps his hands and praises Hakamata for using his Quirk to pull his fellow Pro Heroes out of the way in order to reduce the blast's impact on them. Despite his heavy injuries, Hakamata attempts to fight back and begins sending fiber strings. However, Sensei impales Hakamata from afar. Sensei mentions that he does not need Hakamata's Quirk because it does not suit Tomura’s personality.

Katsuki materialization from the black liquid in front of Sensei catches the attention of Izuku's group. Sensei apologizes to Katsuki as Tomura, Kurogiri, and the Vanguard Action Squad materialize from the black liquid as well. Sensei sees that his apprentice, Tomura, has failed again. However, Sensei is neither angry nor disappointed with Tomura and encourages Tomura to try again since he still has the Vanguard Action Squad and Katsuki whom he deemed important. Sensei implores Tomura to continue trying as many times as he likes since everything is for his sake.

Suddenly, Toshinori appears above Sensei and attacks him. However, Sensei blocks Toshinori's attack. Toshinori declares that he will take everything back while Sensei wonders if Toshinori will attempt to kill him again.

Toshinori and Sensei clash, which creates a shockwave that sends Katsuki, Tomura, and the Vanguard Action Squad backwards. Both Sensei and Toshinori criticize each other for becoming weaker. Toshinori declares that he will save Katsuki and will not repeat the same mistake as he did five years ago and this time he will definitely put Sensei behind bars along with the League of Villains. Toshinori charges at Sensei. However, Sensei sends a huge blast wave at Toshinori, causing the Symbol of Peace to be sent flying away at great force. Sensei's blast wave attack not only hits Toshinori but destroys several buildings in the process.

Katsuki becomes concerned, but Sensei tells Katsuki not to fret since his blast wave attack is not strong enough to kill All Might. Sensei orders Tomura to escape along with Katsuki and comments that his black liquid warping Quirk will not help Tomura and the League of Villains escape. Sensei uses a Quirk that forcefully activates Kurogiri's Warp Gate, which causes a portal to open. Sensei orders the League of Villains to escape into Kurogiri's portal. Suddenly, Toshinori reappears onto the battlefield, refusing to allow Sensei to escape and charges at him. Before heading into battle, Sensei tells Tomura that he can still grow stronger.

Toshinori and Sensei clash once again. Meanwhile, Katsuki is fending off some of the Vanguard Action Squad; Toshinori attempts to help Katsuki only for Sensei to intervene and stop him. Suddenly, Izuku, Eijirou, and Tenya appear above in the air; Sensei sees the trio and attempts to attack them, but Toshinori intervenes by punching Sensei.

Katsuki manages to escape along with Izuku and his friends. Now that the tables have turned, Sensei sees that they no longer can secure victory due to Katsuki's rescue and that most of the Vanguard Action Squad is unconscious. Sensei decides to save Tomura and the Vanguard Action Squad. Sensei forcefully activates Kenji's Magnetism. Before Tomura can attack Gran Torino, he and the Vanguard Action Squad are magnetically pulled into Kurogiri's Warp Gate. As he is being sucked into the Warp Gate, Tomura calls out to his teacher concerned for his safety. Before Tomura teleports away, Sensei tells Tomura to continue the fight. Tomura and the unconscious Kurogiri are teleported away by the Warp Gate, causing the portal to disperse.

Toshinori charges at Sensei, but Sensei uses his Transmission Quirk to teleport Gran Torino in front of him, using the elderly Hero as a human shield which causes Gran Torino to take Toshinori's attack instead. Sensei expresses his hatred for Toshinori as he is the one who brought down his comrades in the past and while he descended into darkness, Toshinori rose to the top as the Symbol of Peace. Sensei prepares to fire his blast wave move, intending of blowing away Gran Torino and Toshinori at the same time. However, Toshinori pulls Gran Torino away and uses Detroit Smash to cancel out Sensei's blast wave move.

Sensei sees that his destruction of the city has brought chaos and decides to put the innocent civilians in danger so that Toshinori will not be able to fight at full strength. Furious with Sensei's sadism, Toshinori grabs his arm while throwing Gran Torino away for safety. Toshinori admonishes Sensei for all the despicable crimes he has committed and for his misanthropy.

Toshinori punches Sensei in the face, shattering his mask; however, Toshinori's punch was not strong enough to finish off Sensei. As Gran Torino calls out to him, All Might's face reverts to its true form. Sensei says that Toshinori would not be the first to criticize him as he has heard those same lines before, from the previous One For All successor: Nana Shimura.

Toshinori is angry at Sensei for mentioning her name. Sensei notes that Nana was all bark and no bite, only going on about her ideals, and was not even strong; he mocks her for her uselessness and mentions that she died an embarrassing, shameful way. Furious, Toshinori prepares to attack Sensei. However, Sensei uses his blast wave technique against Toshinori, causing the hero to be blasted into the air. Gran Torino catches Toshinori and lands him to safety on the ground.

Sensei decides to sever the trust in Heroes once and for all. He once again expresses his hatred for All Might due to taking something away from him and wants him to die in the most gruesome way possible. He fires another blast wave attack at Toshinori, who, seeing that an innocent civilian is trapped under rubble behind him, blocks Sensei's blast wave attack and saves the civilian from being harmed. However, Toshinori expends the last of his power and reverts to his true form. Sensei relishes in the fact that Toshinori's true form has been exposed for all to see.

Everyone around the country sees Toshinori's true form and begins panicking. Sensei mocks Toshinori for the pitiful state he is in. However, Toshinori does not care about his rotting body nor his exposure to the world and declares that his spirit burns strongly which is what truly matters. Wanting to break his spirit, Sensei reveals that Tomura is Nana's grandson. Toshinori is demoralized and refuses to believe, but Sensei tells him that it is the truth. Sensei wonders why Toshinori is not smiling and sarcastically remarks about All Might's smile, which is something Nana would always do. Toshinori's spirit is greatly demoralized by Sensei's sarcasm while Sensei continues relishing in Toshinori's pitiful state.

Invigorated by the civilian, Toshinori activates One For All throughout the right side of his body, transforming it into its Hero form. Toshinori smiles and states that Heroes have many things to protect which is why they do not lose.

Quirk and Abilities
All For One (オール・フォー・ワン): Sensei's Quirk allows him to steal people's Quirks and renders them the user's own. This Quirk can also transfer and grant Quirks (stolen by All For One) to other people, he can even combine his stolen Quirks to create powerful and devastating attacks. Sensei has stolen a variety of Quirks with his ability:


 * Search (サーチ): Sensei stole this Quirk from Ragdoll. With this Quirk, Sensei can observe and monitor up to 100 people at a time, including their location and weak points.


 * Transmission (転送): Sensei can produce a black liquid that acts as a portal, similar in nature to Kurogiri's Warp Gate. It appears Sensei can use this Quirk on a large scale as he produces multiple black liquid portals that transport dozens of Noumus to the League of Villains' hideout. Like Kurogiri's Warp Gate, this black liquid can also teleport people as seen when Katsuki is dissolved by the black liquid. This black liquid warping Quirk, however, has many limitations: this Quirk is not a co-ordinate based warping Quirk and can only warp things to and from his location. Also, the warping only works if it is used on someone with whom he has a close relationship.


 * Forcible Quirk Activation (個性強制発動): Sensei processes a Quirk that allows him to forcefully activate someone's Quirk against their will, whether they are conscious or not. This Quirk creates vain-like appendages that attach to the target and activate the target's Quirk. These vain-like appendages can also be used for offensive purposes. Sensei used this Quirk to forcefully activate the unconscious Kurogiri's Warp Gate and made him create a portal.


 * Levitation Quirk: Sensei is capable of levitating in mid air.


 * Life Extending Quirk: Sensei possesses unnatural longevity through the usage of an as of yet unknown Quirk, being older than any other human.


 * Atmospheric Compression (空気を押し出す):


 * Locomotive Corkscrew (筋骨発条化):


 * Explosiveness (瞬発力):


 * Muscular Enhancement (膂力増強): This Quirk seemingly increases the strength of Sensei's muscles, giving him superhuman strength.


 * Impact Reversal (衝撃反転): This Quirk seemingly enables Sensei to reverse the impact of an attack and make the opponent suffer from it.

Overall Abilities: Sensei is extremely powerful as he battled Toshinori Yagi when he was in his prime and gave him a grievous wound (which would limit Toshinori's usage of One For All). Sensei is able to easily defeat Best Jeanist, the number four Pro Hero, without any trouble.

Genius Intellect: Sensei possesses a genius-level of intellect, possibly due to his advanced age and life experience. He is also the true mastermind behind the League of Villains, being the one who is pulling the strings. He also seems to possess a vast knowledge about Quirks.

Immense Speed: Sensei has incredible speed as he completely destroys the League of Villains' warehouse, defeats all the Pro Heroes there, and deals significant damage to the surrounding area in less than a split second.

Battles

 * All Might vs. Sensei: Draw

Tomura Shigaraki
Tomura is Sensei's successor. It was Sensei who rescued Tomura from an incident during his childhood. Sensei deeply cares for Tomura and is proud of Tomura for being able to execute a plan to achieve a goal on his own. He is livid when the Pro Heroes get in Tomura's way and rescues Tomura and his subordinates from the clutches of the Pro Heroes.

Toshinori Yagi
Sensei detests Toshinori as he is the One For All successor who incapacitated him and killed his comrades. All of these actions have caused Sensei to loathe Toshinori; Sensei wastes no time in belittling and ridiculing Toshinori during their confrontation, even relishing in breaking Toshinori's spirit by revealing that Tomura is Nana's grandson.

Nana Shimura
Sensei thinks of Nana to be a pitiful woman and mocks her for being all bark and no bite, ridiculing her ideals and mocking her lack of strength.

Trivia

 * Sensei's black ornate mask and life support system is most likely inspired by Darth Vader's armor from the Star Wars franchise.

Quotes

 * (To his doctor, in regards to Tomura Shigaraki) "I know that boy will rise to the occasion. He was born twisted. So enjoy it while you can, All Might... This transient peace of yours!"


 * (To Tomura Shigaraki) "You've failed again, Tomura. But you mustn't lose heart. There will be more chances to set things right. That's why I've brought along your little band. And the boy...because you determined that he is an important pawn. So go and try again. That's what I'm here to help you to do. It's...all...for you."