No One's P.O.V.
Izuku Midoriya, the ninth holder of One for All, was currently walking to ground beta. This is because he has been called for some training by his mentor and idol and dad, All Might. He was pretty excited because recently, when he has been called for training, he was able to learn some new tricks with his quirk like how he learned his Airshot.
As Izuku turned the corner into ground beta however, he was met with a sight he wished he would never see; All for One was using one of his quirks stabbing All Might. As soon as Izuku saw this he ran over to All Might, unknowingly activating Full Cowling to his recent maximum of 30%, and was instantly at All Might's side. He quickly started to tell All Might, "Please, All Might don't die. I'm not ready to take him on. I'm not finished with my training.". All Might, knowing he's gonna die really soon said one last thing to Izuku. " My boy, I am sorry I couldn't train you to your full potential, but right now you have to be... No! You ARE strong enough to end All for One's reign in the villain world. You have to kill him. If anyone harasses you about it tell them that I told you to do it. *cough cough* And please tell Inko that I love her. I will see you again someday, my son.". After saying this he passed away in izuku's arms. All for One, who like anime villains do, waited patiently for All Might's speech to end so he could give his two cents on it. " So, you see that buffoon as your father. To say that it isn't upsetting to hear that would be a lie". Izuku, confused, asked why it was upsetting to All for One and was met with the response "It is upsetting because your real father has been here this whole time and hasn't been acknowledged once. You see Izuku, I am your true father, Hisashi Midoriya.
Izuku then asked why All for One left him and his mom when he was diagnosed quirkless. All for One just replied "All i needed from that relationship was your quirk. You see, my quirk was only able to hold two quirks other than itself and i had to give one away or else I would have drawbacks, but your quirk got rid of that feature so I could hold many quirks and could give many at the same time. So I stole your quirk, and started making the Nomu from the USJ. If I recall, that nomu lowered All Might's time limit which went to zero during our fight in Kamino Ward. If i didn't have your quirk All Might would have had time left to be able to take me down. so in the end it was your quirk that killed All Might and has been creating those nomu's that have been terrifying the country.
Izuku was pissed so he yelled " YOUR'E THE REASON I WAS BULLIED MY WHOLE LIFE! ALL MIGHT DIDN'T HAVE TO DIE SO EARLY! YOU'LL PAYYYYY! FULL COWLING 100%!". All for One, ready for the final battle between All for One and One for All, activated every single one of his combat oriented quirks but before he could react, Izuku was infront of him and yelled DETROIT SMASSSSHHHH! and punched him back about 10 feet. All for One quickly rushed back to izuku and used a kind of impact storing quirk and used the energy stored to hit Izuku into a building. Then Izuku used his shoot style of All for One and broke his skull, but not before taking a punch to the gut that would leave him unconscious for atleast a month. His attack ended up killing All for One. Izuku sighed and lied next to All Might, put into comatose.