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Sensei (in Japanese: 先生 Sensei), who's real name is All For One (オール・フォー・ワン Ōru Fō Wan), is one of the main antagonist of Boku no Hero Academia (AKA My Hero Academia in English) Manga and Anime series. A man with a completely deformed face who was defeated by the hero, All Might, and founded the League of Villains with Tomura Shigaraki as his successor and the main force of the organization.
In the past he appeared as a normal young man with a notable suit and short hair, however his face is still not seen completely.
After his crushing defeat, he appears completely different then before, his face is deformed with a scar on his neck and the assence of two eyes, he also has two tubes connected to his throat which allows him to breath and act as the mind of the organization.
Until now All For One showed to be a mysterious and sinister individual, which is able to create complex and elaborate plans in a little matter of time and then order Tomura to fulfill them.
Power and Abilities
In the past he was a very powerful individual who managed to wound All Might and block his One for All ability, his main ability is the opposite of that of his nemesis, which is All For One, this ability allowed him to steal people's Quirks and render them as his own. He has also multiple powers.