Another potential antagonist could be a rogue shinobi who has a vendetta against the Uzumaki clan from the past. He doesn't want to see the clan restored and uses his own dark jutsu and a network of followers to try and stop Naruto at every turn. He might be jealous of the power the Uzumaki once held and fears they will regain that power.
It could be a group of rogue ninja who are after the Uzumaki's powerful sealing jutsu. They see it as a way to gain unlimited power and rule the ninja world, so they target the Uzumaki clan, which makes Naruto their main enemy as he stands in their way.
Danzo could be a main antagonist. He was always paranoid about the Uchiha clan's power and was involved in many of the events that led to their downfall. In a fanfiction where Naruto is trying to save the clan, Danzo would likely oppose Naruto's efforts as he sees the Uchiha as a threat to his own power and the village's stability in his own twisted way.
It could be a group within Naruto's own clan who have turned against the rest of the clan due to some ideological differences. They might want to use the clan wars as an opportunity to take over the clan and change its values. Another possibility is a mysterious and powerful ninja from another land who has his own motives for causing chaos during the clan wars.
Perhaps an old enemy of the Uzumaki clan, long thought to be defeated, resurfaces. They see Naruto as a threat because of his position as the heir and aim to eliminate him before he can fully embrace his Uzumaki heritage and power. This could be someone with a vendetta against the Uzumaki for past events, like a clan that was defeated by the Uzumaki in the past and now wants revenge.
The main antagonists could be other powerful clans in the Hidden Leaf Village. For example, the Uchiha clan (if they were still around and had some grudges or power struggles). They might see the restoration of the Hinata clan as a threat to their own status and power within the village.
It could be some rogue ninja groups. They might fear that a restored Uzumaki clan would disrupt the current balance of power in the ninja world. These groups could target Naruto and his supporters, stealing resources meant for the clan restoration or spreading false rumors about the Uzumaki clan to turn public opinion against them. Also, there might be some corrupt politicians within Konoha who oppose the restoration act for their own self - serving reasons.
The Sound Ninjas could be great antagonists. They could use their own unique parkour - like skills to try and stop Naruto. They might be chasing him through the forest, and Naruto has to use his parkour skills to outmaneuver them.
Maybe some corrupt officials within the prison system itself. They oppose Naruto's more humane and reform - focused approach to prison management. They might try to undermine him at every turn, for example, by cutting off resources or spreading false rumors about him among the prisoners.
Maybe a group of dark - type Pokémon that have banded together and are trying to overthrow Arceus. They view Naruto as an easy target at first, but quickly realize he is a formidable opponent with his ninja skills and new Pokémon - related powers. They would constantly try to undermine Naruto and his efforts to protect the Pokémon world.
The Akatsuki could also be antagonists in Uzumaki clan revenge fanfiction. They were after powerful ninja and the Uzumaki clan was full of power. They could have been the ones who initiated the attack on the Uzumaki clan to get their hands on things like the Uzumaki's powerful chakra or their sealing techniques. And then there might be a secret group within the Leaf Village itself that was involved in the Uzumaki clan's downfall, perhaps out of fear of their growing influence.