My Hero Academia is setting up for the end of its third season, and now that the Hero License Exam has wrapped its time to look more toward the future. A future All For One has already planned for far in advance.
The latest episode had All Might confronting his nemesis for the first time since their fateful bout, and All For One proved he's just as deadly as he's ever been.
When All For One was defeated, he didn't seem to dejected by it and was confident that he raised Shigaraki enough to take over his villainous dreams. This continues into the latest episode, where despite being locked into the impenetrable prison Tartarus All For One sits as confidently as ever. Taunting All Might much in the same way he had done during their fight, All For One sets up an ominous future.
Mentioning how stifled he feels in the prison, he tries to get news of the outside out of All Might. All Might wants to know where Shigaraki is, and just what All For One's goal is, but All For One says it doesn't matter as All Might would never understand him anyway. Wanting to become an "Evil Devil King" All For One started raising a successor when All Might came into the picture.
Knowing that his time would soon come to an end, he raised Shigaraki to take over his ideals. He even makes a guess as to the nature of the outside world, and implies that it was all a part of his plan. Noting that the media's unease of All Might's retirement along with a lack of faith in Endeavor as a replacement has them complaining about the unity of the hero society as a whole (which the new Hero License Exam is trying to fix).
Those on the outside of these boundaries will begin to distrust heroes even more, and are starting to organize in order to change society how they wish to. The villains will fight amongst each other in order to be the group that comes out on top, and he's confident Shigaraki will be the one to do so. All For One has calculated all of this to take place after All Might's retirement, implying that him being captured was part of the plan as well.
At the end of the day, he just wants All Might to suffer as he's forced to powerlessly watch future heroes like Midoriya struggle against future major villains like Shigaraki. No matter where he is, All For One is always trying to figure out how to damage All Might the most. It's a frightening prospect.
My Hero Academia was created by Kohei Horikoshi and has been running in Shueisha's Weekly Shonen Jump since July 2014. The story follows Izuku Midoriya, who lives in a world where everyone has super powers, even though he was born without them. Dreaming to become a superhero anyway, he's eventually scouted by the world's best hero All Might and enrolls in a school for professional heroes. The series has been collected into 19 volumes so far, and has been licensed by Viz Media for an English language release since 2015.