Who could be the main antagonist in a 'naruto devil hunter fanfiction'?

It could be a powerful devil who sees Naruto as a threat to his rule in the devil realm. Maybe this devil wants to use Naruto's power for his own evil purposes and Naruto has to resist.

It could be a rogue hunter nin who doesn't like the idea of Naruto, an outsider, joining their ranks. This rogue hunter nin might see Naruto as a threat to their power and influence within the group.

It could be a rogue ninja who has mastered the devil breakers in a very dark way. He might use them to gain power and control over the ninja world, seeing Naruto as the main obstacle to his plans.

It could be a powerful demon lord who wants to conquer both the Naruto universe and the Devil May Cry world. This demon lord might have the ability to manipulate chakra and also use demonic powers, making it a formidable foe for both Naruto and Dante.

It could be a rogue hunter who has his own twisted ideas about the use of Nen. This hunter might see Pokkle and Ponzu as obstacles in his quest for power and knowledge. He could try to capture them to steal their Nen abilities or the information they have about certain areas of the Hunter x Hunter world.

There could be a group of poachers who are not just after regular game but are also involved in some dark magic. They oppose the hunters and especially Percy when he tries to stop their illegal and dangerous activities. They might have powerful backers or magic items that make them a formidable foe for Percy and the other hunters.

It could be an evil poacher who wants to capture all the dalmatians for their fur. He would be a formidable antagonist for the hunter as he has his own set of cruel hunting skills.

It could be someone from the Naruto universe who doesn't like Naruto's newfound fascination with Aku. For example, Danzo might see Naruto's interest in Aku as a threat to the stability of the village and try to stop Naruto from further exploring Aku - related things. So, Danzo could be the main antagonist in this case.

It could be a new character created specifically for the fanfiction. This character might be an outcast from a powerful clan in the Hunter x Hunter world, with a grudge against the hunters, thus being named the 'white devil' due to their menacing and unpredictable nature.

It could also be a human scientist who has been experimenting with demonic energy. He becomes corrupted by this power and decides that he should control both the human and demon worlds. He sees Devilman and Devil Lady as obstacles in his path and uses his scientific knowledge and newfound demonic powers to try and defeat them.