Deku's ultimate fate was unexpected for many fans, but there's an early piece of information that hinted at what would become ...

But to reach Shigaraki, Izuku will need to keep All For One off his back, and take the villain out of the equation: so why not let Bakguo (All Might’s other protege) be the one who does it?

This Quirk gives All Might exceptional strength, speed, endurance, and agility, making him the number one hero in his prime.