There could also be non - human enemies. For instance, a powerful and malevolent magical creature that has been awakened or angered by the changes in the wizarding world brought about by Harry and Hermione. Their daughter, being in the spotlight as their child, becomes a target as the creature believes she can be used to reverse these changes or is simply a symbol of the 'human interference' it hates.
A new dark wizard could rise. This wizard might be jealous of the fame and power that Harry has, and seeing his daughter as an extension of that, decides to target her. Maybe this new dark wizard is seeking to gain control over the wizarding world and sees her as a key obstacle in his path.
There could be a new dark wizard or witch who is jealous of the Potter family's legacy. They might target Harry Potter's daughter to try and bring down the family name and prove their own power.
The First Order could still be a threat. They might see her as a symbol of the Resistance and try to eliminate her. Or it could be a new Sith cult that has risen in the ashes of the old Sith order.
Voldemort's remaining followers could be her enemies. They might be planning something new and Hermione, as a spy, would be trying to stop them. Also, some corrupt Ministry of Magic officials who are up to no good. They would see Hermione as a threat to their secret operations.
The remnants of Voldemort's followers could still be a threat. They might see the third child as a symbol of the new hope in the wizarding world that they want to destroy. Maybe they believe that the child has some sort of power that could ultimately be used to completely wipe out their dark ideology, so they target the child.
The Death Eaters could still be a major threat. Even with Voldemort gone, some of them might be trying to revive the dark ways and see the wizard king as a big obstacle in their path.
The obvious enemies could be the Ministry of Magic. If Harry is stealing things, even if for good reasons, they would see him as a criminal. The Aurors would be sent after him. Another potential enemy could be some of the dark wizards who might want the same items that Harry is after. They would not want Harry to get in their way and would try to stop him or even capture him to get information on the whereabouts of the valuable items.
Another potential enemy could be a group of pure - blood supremacists who don't like the idea of the White Knight, who might be a symbol of change and equality in the wizarding world. They would try to undermine the White Knight's efforts to make the wizarding world more inclusive.
Ginny Weasley could be a likely candidate. She already has a connection with Harry in the original series. Luna Lovegood might also be included. Her unique perspective and kind nature could make her an interesting addition. Cho Chang could be another possibility as she and Harry had some romantic history before. And maybe even some of the lesser - known witches from different houses who admire Harry for his heroic deeds.
The Ministry of Magic would likely be an enemy. They are all about maintaining order and the Demon Prince's actions might be seen as a threat to that order.
Voldemort or his remaining Death Eaters could be the main enemies. They would see Harry's new blade master abilities as a threat. Another potential enemy could be a dark wizard from a foreign land who is jealous of Harry's power.