The Phantom Troupe could be antagonists. They are a group of dangerous criminals in the Hunter x Hunter world, and they might see Kaito as a threat or a target for their own purposes. Another potential antagonist could be some of the more corrupt members of the Hunter Association who might not like Kaito's independent ways. There's also the possibility of new, original antagonists created specifically for the fanfiction, like a powerful dark magician who wants to use Kaito's power for his own evil plans.
A possible plot for 'Kaito Hunter x Hunter fanfiction' is that Kaito enters a special tournament in the Hunter x Hunter world. This tournament has rules and challenges that are different from the normal ones. He meets new and interesting characters during the tournament, some of whom become his friends and some his enemies. As he progresses through the tournament, he uncovers a conspiracy that is related to the very foundation of the Hunter x Hunter world. He then has to decide whether to expose it and risk his life or keep quiet and let the conspiracy continue.
One way is through intense training. In fanfiction, a character might undergo extreme physical and mental training regimens that push their limits. For example, Gon could train in isolation with more powerful nen masters, learning new and advanced nen techniques that weren't shown in the original series. This could include more complex manipulation of his aura, like creating multiple types of nen beasts for different purposes.
The 'hunter x hunter meruem x oc fanfiction' often explores unique relationships. It might show how an original character (OC) interacts with Meruem. Maybe the story focuses on the OC influencing Meruem's view of the world, or vice versa. It could also be about their adventures together in the complex world of 'Hunter x Hunter'.
There's a fanfic called 'Meruem's New Path'. In this story, Meruem survives his battle and tries to find a new purpose in the world of Hunters. It has a unique plot that keeps you hooked from start to finish. The writer does a great job of staying true to Meruem's complex personality.
I really like 'A Hunter in Beacon'. It starts with a Hunter x Hunter character somehow ending up in the RWBY universe at Beacon Academy. It has a lot of action scenes that are both exciting and true to the nature of both franchises. The author does a good job of making the interactions between the characters from different universes believable.
One great Neferpitou fanfiction is 'The Redemption of Neferpitou'. It shows an alternate storyline where Neferpitou tries to understand the concept of humanity more deeply. Another interesting one is 'Neferpitou's Journey'. It explores Neferpitou's growth and development in a world post - Chimera Ant arc. There's also 'Neferpitou and the Lost Soul' which delves into Neferpitou's encounter with a mysterious being that challenges its very nature.
There's also 'Hunter x Hunter meets Ranma 1/2: The Adventure'. This one takes a more light - hearted approach. It has some really funny moments as the characters from both series misunderstand each other's cultures. The fanfic does a great job of exploring the comical side of a crossover.
One great 'Hunter x Hunter Chrollo Fanfiction' is 'Chrollo's Redemption'. It explores an alternate path for Chrollo where he tries to atone for his past sins. The story has really good character development and the author does an amazing job of getting into Chrollo's psyche.
One great 'Naruto and Hunter x Hunter' fanfiction is 'The Cross - Over Quest'. It combines the unique worlds and power systems of both series in an interesting way. The main character, who has abilities from both Naruto and Hunter x Hunter universes, embarks on a journey to save both worlds from a common threat. It's full of action - packed scenes and well - written character interactions.