Warning! Spoilers ahead for My Hero Academia chapter 326!
All Might has been desperately trying to find a purpose in My Hero Academia ever since Deku went on his own to face All For One, and just when he gave himself his own mission, his insecurities get in the way.
All Might truly fell from grace when his final confrontation with All For One exacerbated an earlier wound dealt by the very same villain from a previous encounter, forcing him into early retirement. This not only affected All Might but placed a heavyweight on his student, Deku, who was now the recipient of All Might's power and therefore the only hero who could take down All For One. All Might attempted to help Deku as best he could during this time, but when Deku brushed All Might aside, the former number-one hero hit rock bottom.
After class 1-A finally drags a begrudging Deku back to U.A. High, All Might is able to shift his focus and takes it upon himself to check on the so-called hero-hating groups who have refused shelter in chapter 326 of My Hero Academia. This is actually a sound strategy as no one would ever expect that this frail, gaunt, and haggard man could be the former number-one hero. If anyone could convince people who hate heroes to help themselves, it's someone who doesn't look like a hero. But even in this task, which ironically is the best possible mission he could ever take on in this pathetic state, All Might fails. But it's not just because he's physically incapable of completing the mission. He arrives at a place where all of his failures come to meet him: A torn piece of Deku's mask and a vandalized All Might statue with a sign dangling around its neck mocking one of his signature phrases: "I am not here."
Coming face to face with his two failures in physical form is obviously too much for All Might to handle as he can only focus on them instead of finishing his own task he gave to himself. Deku's mask is a reminder of how he had been unable to help his student when he needed him most even though he was the reason why Deku was in such dire straits in the first place. The statue, meanwhile, sheds light on his failure to achieve what All Might was meant to deliver and, ironically, what influenced Deku to become a hero: How All Might could miraculously bring hope to the utterly hopeless just by smiling and saying "I am here." All Might was a symbol of hope for those at their worst in their most desperate of times. But his vandalized statue just shows how he's failed in that regard.
It's ironic that mangaka Kohei Horikoshi put All Might's latest failures on total display for the reader to behold but withheld what is now My Hero Academia's greatest mystery when he somehow defeated thugs in his weakened form. All Might needs redemption, and hopefully, he can start by finishing what he started: To help those who don't want to be helped.