It's hard to say for sure. Deku has grown a lot, but All For One is a powerful villain. It depends on various factors like their current abilities and the circumstances of the battle.
As of now, Deku is very much alive in the manga. The plot hasn't reached a point where he meets such a fate. Usually, main characters like Deku have significant story arcs and aren't easily killed off.
In 'All for One Deku' fanfiction, it's interesting to explore the new relationships Deku would form. For example, his interactions with villains who were once on the opposite side of him. Also, the power dynamics shift. Instead of being the underdog hero, he could potentially become a more complex and morally ambiguous character with All for One's powers. His internal struggle between his original self and the new, darker influence can create really engaging storylines.
The main differences are in their expressions and some minor details of personality. In the manga, Deku might seem a bit more intense, while in the anime, he's sometimes presented a bit softer.