Maybe Orochimaru's former followers who are still lurking in the shadows. They see Naruto as a threat and Hinata as an easy target to get to Naruto. Another possibility could be some power - hungry shinobi from other villages who view Konoha as weak after the Pain incident. They might target Naruto and Hinata as key figures in Konoha's future to try and undermine the village's rebuilding efforts.
In this type of fanfiction, the antagonists could be a new group of rogue ninjas. They are inspired by Pain's ideology but take it to more extreme levels. They target Hinata to get to Naruto, knowing that Naruto cares deeply for her. Also, there could be some internal political opponents in Konoha who oppose Naruto and Hinata's relationship, fearing it could disrupt the traditional power balance in the village.
It could be some rogue ninjas who are against Naruto's new peaceful policies as Hokage. They might see Hinata as a weakness to be exploited to get to Naruto.
One possible antagonist could be a jealous student. Maybe someone who has a crush on Hinata and doesn't like Naruto getting close to her. This student could try to sabotage their projects or spread false rumors about them at the academy.
Another type of antagonist could be a strict professor who doesn't like Naruto's carefree attitude and Hinata's association with him. The professor might try to give them a hard time, like assigning them extra difficult projects or being overly critical in class, which becomes an obstacle in their college life and relationship.
The Akatsuki remnants could still pose a threat. Members like Sasori or Deidara might have had backup plans or followers who now want revenge for the Akatsuki's downfall. They could target Naruto specifically, seeing him as the one who brought down Pain and disrupted their plans.
It could be some new group that emerged due to the changes in the ninja world over time. They might oppose the way Naruto and Hinata's village is being run and want to impose their own ideals.
It could be some of the old - school ninja clans who are against the new order Naruto and Hinata are trying to establish. They might see their rule as a threat to their traditional power and influence.
Hinata saving Naruto from Pain in fanfiction can take on many forms. It could be that Hinata has been secretly training and has a new set of abilities that she unleashes to save Naruto. This not only changes the course of the battle but also the dynamics between the characters. Fanfic writers might also add some emotional elements, such as Hinata's inner thoughts and feelings during the rescue. This makes the story more engaging and gives readers a fresh perspective on the Naruto - Hinata relationship.
One common theme is redemption. Pain is often depicted as a character who can be redeemed through his interactions with Hinata. For example, Hinata's unwavering belief in the good of people might make Pain question his own actions.
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.
There could be other ninja from rival villages who act as antagonists. They might see Naruto as a threat and target Hinata to get to him during the Chunin Exams. These antagonists would create conflict and danger for Naruto and Hinata, forcing them to grow and rely on each other more.