There are fanfictions where the main characters react to different versions of their powers. For example, Gon and Killua reacting to a more powerful or darker version of their nen abilities. This can lead to interesting character development as they grapple with what they could become. It also allows the author to explore different power - up scenarios in a unique way.
Since there's no official ending yet, it's hard to say. But if it follows the pattern of the series so far, it could be very satisfying. The series has been great at character development, so seeing all the characters reach a proper conclusion would be great.
Another way is to join Hunter x Hunter fan communities on social media platforms like Reddit or Facebook. Ask the members there for recommendations on good reaction fanfictions. They might be able to point you to some hidden gems that you wouldn't find through a simple search.
I'm not entirely sure as the 'Hunter x Hunter' manga and anime are still ongoing with no official full ending as of now. But generally, it might be about the conclusion of Gon's journey, his growth as a Hunter, and how he resolves the various relationships and challenges he has faced throughout the series.
The Hunter x Hunter manga is unfortunately not complete. The author has faced various issues that have led to intermittent breaks and an unresolved storyline.