In this fanfiction, it's possible that there are individuals who are power - hungry and envy the unique powers of the Kyuubi's daughter. These individuals could be from within the village or from other places. They might try to sabotage her growth, spread false rumors about her, or even directly attack her. Additionally, there could be remnants of old enemy organizations that see her as a symbol of the new strength of the Leaf Village and want to destroy her to weaken the village as a whole.
Well, there could be an underground organization that wants to capture her for their own dark purposes. Maybe they want to extract the Kyuubi's power from her and use it for some evil plan. Also, some traditionalist shinobi within the Leaf Village who oppose any change in the status quo regarding the Kyuubi might also act as antagonists. They might not accept the idea of the Kyuubi having a 'descendant' in a sense, and would try to undermine her at every turn.
One possible group of antagonists could be those in the Hidden Leaf Village who still hold a grudge against the Kyuubi. They might see the daughter as a threat and try to get rid of her. Another could be rival villages that fear the power she might possess and see her as a weapon that could be used against them in the future, so they would try to eliminate her before she becomes too powerful.
Another potential antagonist could be an inner demon within Naruto that is a manifestation of the Kyuubi's corruption. This inner demon could constantly be battling Naruto's good side, trying to take over completely. And there could be characters who misunderstand Naruto's situation and side with the forces that are trying to 'contain' or 'destroy' Naruto because they believe he is a lost cause due to the Kyuubi's corruption.
The Akatsuki could still be the main antagonists. Even though Naruto has accepted the Kyuubi, they might see his new power as a greater threat or a valuable asset to capture. They could try to take the Kyuubi from Naruto to use for their own evil purposes.
Often, it could be the Akatsuki. They are always after the power of the tailed beasts, and with Naruto being protected by the Kyuubi, they would be major antagonists. They might come up with new and devious plans to try and get to the Kyuubi within Naruto.
Often, the Akatsuki still remain as main antagonists. Since Naruto's fusion with the Kyuubi makes him more powerful, they would be even more interested in capturing him for his power.
The Akatsuki could still be the main antagonists. Even with Naruto's training by the Kyuubi, they would be after the tailed beasts. Their goals of collecting all the tailed beasts would put them in direct conflict with Naruto. And they have some really powerful members like Pain and Itachi.
The main antagonists could be the villagers who fear Naruto's mini Kyuubi form and try to drive him out of the village. Their prejudice and fear act as a major obstacle for Naruto, who just wants to be accepted.
It could be Orochimaru. He's always been after power and Naruto's unique abilities would be very appealing to him. So the fem Kyuubi would have to constantly be on guard against Orochimaru's schemes.
It could be a new group of rogue ninjas who oppose the ideals of the Hidden Leaf Village. They might target Kakashi's daughter because of her connection to Kakashi and Naruto, seeing her as a symbol of the village's new generation of strength.
The main antagonists could be those who envy her wisdom. They might be jealous of the attention she gets or the power that her wisdom gives her. So, they try to undermine her at every turn, spreading false rumors about her or trying to make her look foolish in front of important people.
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.