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Honestly the source material for the dialogue is perfect. All Might has to hold on and win the fight to reprimand and train his successor until he is ready, and in order to do this he must use up all remnants of his original power to take down the most threatening villain his successor will ever face. All ended with an epic "United States of Smash!" The final exchange can actually be read as:
"Farewell All For One, [All for One being defeated in the moment - a literal good bye.] UNITED STATES OF SMASH! [The action doing the above.]
"Fare Well, One for All" [All Might is passing the mantle on with his hopes to Midoriya. Faring the power well, as it were.]
Additionally, this fight incapacitates the two pillars of the Hero and Villain world respectively, and the next arc actually focuses on the fact the *villain* world is shifting, which was a great plot decision. People expect the hero world to be radically altered and the focus to be there, but the main thrust of the next arc is that villains are in the most flux.
Finally, In the last attack, Toshinori's arm is fully healed by One for All before his final attack on All for One, which symbolically means One for All is not just a strength enhancer based on stockpiling over time, but an actual sort of perfection of the self and combining of wills. It's a transcendent power. This was such an impactful way to illustrate that, and it's why I love the anime because it brings all these concepts in the manga into the foreground.
And then later, when the reporters are making speculations that would cause people to panic, All Might points his finger out and says:
"Next, it's your turn."
Which itself has multiple meanings from character perspectives in world. All Might simultaneously dampens the panic the media would have incited, and passes a message on to both criminals and Midoriya,
It's incredible writing, and the animators are adapting it amazingly.