The other villages might become the main antagonists. Naruto, in his new state of hating, could blame the other villages for the overall chaos and conflict in the shinobi world. Their constant power struggles and rivalries could be seen as the cause of his friends' deaths or his own suffering. As a result, he might target them, making them the main antagonists in the 'naruto gives in to hate fanfic'.
It could be the shinobi council. If Naruto gives in to hate, he might view the council as the root of all the problems in the shinobi world. Their decisions, like sending young ninjas on dangerous missions or their political games, could be what Naruto now wants to fight against. So, the shinobi council would be the main antagonists.
The villagers themselves could be the main antagonists. Since Naruto has given in to hate, he may see the villagers' past mistreatment of him as unforgivable. Their judgmental and often cruel behavior towards him in his childhood could now be the reason he turns against them, making them the antagonists in this new narrative.
The village elders or certain hidden factions within the village could be antagonists. If Naruto turns dark because of their actions against him, they would naturally be in opposition to him as he seeks revenge or tries to change the village in a way they don't want.
There could also be some within the wizarding community who oppose Harry learning the Unforgivables. They might see it as a sign that he is turning to the dark side and try to stop him, so they could act as antagonists in the story.
Another possibility is a rival pirate hunter. Someone who is jealous of Sakura's skills or success and tries to get in her way, perhaps by spreading false rumors about her or even directly interfering with her missions.
Well, it could be that Naruto discovers some dark secrets about his family or the origin of the Nine - Tails within him. These revelations make him feel betrayed by those he trusted, such as the previous Hokages or his sensei. As a result, he gives in to hate. He might then form alliances with former enemies who also have a grudge against the established shinobi order, and together they plan to overthrow and reshape the world according to their own, more self - serving ideals.
Danzo could be a main antagonist. He's always been power - hungry and has seen Naruto as a threat to his control over the village. After Pain's attack, he seizes the opportunity to turn the villagers against Naruto.
It could be Frieza. He might be jealous of Vegito's power and decides to target Bulma to get to Vegito. His actions could make Bulma realize the danger she's in because of her association with Vegito, leading her to give up on him.
A jealous classmate could be a main antagonist. This person might be envious of Naruto's popularity and his ability to make friends easily. They could try to spread rumors or sabotage Naruto's projects.
The Akatsuki could still be a major antagonist. Even if Naruto is emperor, they might oppose his rule as it goes against their own goals of chaos and obtaining the tailed beasts.
One possible antagonist could be a jealous noble from Naruto's own kingdom who feels that Naruto doesn't deserve the prince title. This person might try to undermine Naruto at every turn, spreading false rumors about him or trying to sabotage his diplomatic efforts.
Another possible antagonist could be a fellow inmate who has a personal vendetta against Naruto. Maybe this inmate was once on the wrong side of Naruto's actions outside the prison and now sees this as an opportunity for revenge. He could try to undermine Naruto at every turn, from spreading false rumors about him to physically attacking him when the guards aren't looking.