The true face of evil.
Episode 20 of Season 2 (or Episode 33 as a whole) of Boku no Hero Academia (My Hero Academia) picks up with Gran Torino seeing Izuku off with some nagging that he has a lot to learn. He also explains that he didn’t have all that much interest in being a hero in the past and only became one because he needed to be able to use his Quirk freely. He wishes Izuku well and looks forward to the day “Deku” becomes the new Symbol of Peace.
Back with Class 1-A, the young heroes-in-training talk about their experiences. Izuku, Todoroki, and Iida naturally have to keep mum on their fight with Stain and state that Endeavor saved them, but then Kaminari praises Stain for his tenacity in front of Iida. Iida understands why others could see him being cool that way, but Iida decides to keep at working towards being a hero to make up for his past screw-up.
Then they get to do some rescue training in the form of a race. Izuku gaining Full Cowl allows him to keep up pretty well, though he screws up near the end. Bakugo is naturally upset that Izuku had progressed further, copying his movements at that. But All Might has nothing but praise for him and asks to see him after class.
There, All Might explains that his power, which was transferred through DNA, didn’t get passed onto Stain since it has to be done by his wish. However, One For All came from a different Quirk that existed in the past called “All For One”, which could steal the Quirks of others and transfer them to other people. Back in the past, a villain with that name took advantage of that chaotic period by stealing Quirks and using them to get influence.
He gave his brother a Stockpiling Quirk against his will and that merged with his own Quirk that allowed it to pass on other Quirks. The two of them mixed together to become “One For All”. The reason All Might brings the story up is that One For All was meant to defeat the Symbol of Evil, All For One. All Might thought he’d done so in the past, but he’s the one who is behind both the Nomus and the League of Villains, meaning that Izuku must not bear that burden.
Izuku tells him he’ll do his best, but All Might hides some information from him that heavily implies he’ll be dead by the time they’re ready to fight. The episode then ends with a glimpse of All For One, who intends to raise Shiragaki to take his place.
So, this episode was heavy. We not only learn about the man pulling the strings behind the curtain, but also how All Might had beaten his face in so violently that he couldn’t recover from it. At the same time, All Might suffered an injury so severe he has a time-limit.
The opposites, the Symbol of Peace and Symbol of Evil, have been passed on at this point. All For One with Shiragaki and One For All with Izuku. These two have some big shoes to fill, but in this case it probably won’t be until later on in the series. Still there’s something poetic about how from the greatest evil the greatest good emerged.