A new group of rogue ninjas who oppose the idea of a female Hokage could be antagonists. They could be made up of traditionalist ninjas who believe only men should hold power. They would constantly try to undermine the female Naruto's progress, whether it's by attacking her directly or spreading rumors to turn the village against her.
The Akatsuki could be great antagonists as always. But in this AU, they might target the female Naruto specifically because of her potential to change the ninja world in a different way. They could see her as a threat to their plans, especially if she's advocating for more equality among ninjas, which could disrupt the power balance they're trying to achieve.
Sasuke could still be an antagonist in a way. Maybe in this AU, he's more dismissive of the female Naruto because of his own ideas about strength and gender. He might see her as weak at first and that could create a lot of tension between them.
Danzo could be a great antagonist in this 'naruto highschool au fanfiction'. He could be the strict school principal who enforces very strict rules and has a hidden agenda. He might not like Naruto's free - spirited nature and try to expel him. Also, Kabuto could be a student who is under Danzo's influence and causes trouble for Naruto and his friends.
Alois could be a main antagonist. In a high school setting, he might be the jealous rival of Ciel. He could try to undermine Ciel's position as student council president or spread rumors about him. His butler, Claude, would be helping him with his devious plans.
If we swap Star and Marco, then the main antagonists could be those who were previously minor annoyances for the other character. For example, if Marco is now in Star's role, Ludo, who was a main antagonist for Star, could be an even bigger threat as Marco might not have Star's natural magical intuition to deal with him.
He could meet an AU version of Hinata who is more assertive and outgoing. Maybe she's a powerful ninja in her own right and not as shy as in the original story.
A really interesting antagonist could be a mysterious figure from a hidden organization. This person has been secretly observing Naruto's family for a long time. They have a master plan that involves using Naruto's daughter as a key component. Maybe they want to use her unique chakra or abilities for some dark purpose. They would be constantly manipulating events behind the scenes, setting up traps and challenges for her, all while remaining in the shadows, which would make them a very menacing and unpredictable foe.
A group of female ninjas who oppose Naruto's presence in their world could be antagonists. They might believe that his arrival will disrupt their way of life and power structures. For example, a powerful all - female clan that has long held sway in the ninja world might see Naruto as a threat to their dominance.
There could be a powerful and jealous ninja from another village. This ninja wants the power of the Shukaku for himself. He sees the relationship between Naruto and the female Shukaku as an obstacle to his goal, so he devises plans to separate them and capture the female Shukaku, making him a major antagonist in the fanfiction.
One potential antagonist could be a group of rogue ninjas who see Sarada's pregnancy as a sign of weakness in the village. They might try to target her to cause chaos. Another could be a jealous rival who doesn't like the attention Sarada is getting due to her pregnancy and her connection to Naruto.
It could be Orochimaru. He might be interested in the baby's unique genetic makeup, thinking he can use it to create more powerful experiments. He has always been obsessed with power and the baby's combination of Naruto and Temari's abilities would be very appealing to him.
The village elders could be the antagonists. They might have a hidden agenda and want Naruto out of the picture, so they imprison him unjustly.