All For One is the big bad of "My Hero Academia." He and his Quirk of the same name serve as a counterpoint to One For All, which is the name of protagonist Izuku Midoriya's Quirk. Of course, the names of the two Quirks combined are a reference to the motto of the Three Musketeers.
The names All For One and One For All aren't merely literary references, however, but describe the essential nature of each ability. Midoriya's One For All must be passed down from one user to another. Before Midoriya, nine other heroes, including series mainstay All Might, wielded One For All. By contrast, All For One uses his Quirk to steal abilities from other Quirk users, leaving them Quirkless and granting him an additional superpower.
As a result of All For One's ability to both render his opponents powerless and wield multiple powers himself, his Quirk is stronger than virtually anybody else's in the "My Hero Academia" universe. Multiple discussions on Reddit and rankings by sites like CBR and Screen Rant have come to the same conclusion, citing these core reasons. In short, All For One operates on its own set of rules separate from essentially all other Quirks, meaning that from a strict analysis of its potential, it remains the most formidable Quirk in the series thus far.
