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.
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.
If Deku had One For All early, it could either make him a hero sooner or cause him more problems. It might make his enemies step up their game or force him to face even greater threats. It's a fascinating what-if scenario that could go in many different directions.
You can try fanfiction platforms like Archive of Our Own (AO3). There are a large number of fanfictions there, and you can simply search for 'All for One Deku' in the search bar. Another option is FanFiction.net, though the selection and quality may vary.
Another plot could involve All for One somehow transferring a small part of his consciousness into Deku. Deku then has to battle with this foreign presence in his mind while trying to keep his friends and the world safe from the potential chaos it could cause. This would also lead to some interesting character development as Deku tries to resist the dark influence.