Another possibility is a vengeful former Death Eater's apprentice. This person blames Harry for the downfall of their master and the loss of the Death Eater regime. Seeing Harry as a weakened target because of his blindness, they plot to exact revenge on him. They might use dark magic to create illusions and traps specifically designed to disorient Harry, taking advantage of his lack of sight.
A rogue ninja from a formerly warring village could be the main antagonist. This ninja might hold a grudge against the new peace and wants to disrupt it. He could be powerful and have his own group of followers who are also discontent with the current situation.
The plot could revolve around Harry's rehabilitation. Ginny could be by his side, training him to use his other senses. Maybe they work with magical healers who try different spells to restore his sight, but it doesn't work. So they focus on making his life as normal as possible. Ginny would teach Harry how to move around Hogwarts without bumping into things, and they'd have a lot of cute, clumsy moments in the process.
A new supervillain could emerge. Maybe a scientist who got access to some of the leftover technology from the Civil War battles and uses it to create a powerful weapon. He then targets Spiderman because he represents the superhero community.
It could be a power - hungry shinobi from another village. This shinobi sees Naruto's exile as an opportunity to gain more power and influence in the ninja world. He might try to hunt Naruto down to prove his own strength or to steal Naruto's secrets.
Perhaps a secret organization within the Hidden Leaf that wants to take over the village. They use Naruto as a scapegoat, getting him banished so they can carry out their evil plans without interference from Naruto. They would be the main antagonists as they are the ones behind the false accusations and the push for his banishment.
Perhaps a new, unknown force. With Naruto gone, a previously hidden group with a vendetta against the ninja villages could emerge. They might blame the villages for the destruction caused during the war and see Naruto's death as the perfect time to strike, when the villages are still recovering and vulnerable.
Maybe it's an old enemy who survived the war and has grown stronger. They hold a grudge against Natsu and his friends and are now seeking revenge. For example, if there was an enemy that was thought to be defeated before the war but managed to survive and is now back with a vengeance.
Perhaps a long - lost relative of the Potter family who feels they were unjustly excluded from inheriting the manor. This relative could be jealous of Harry's status and the wealth associated with the manor. They might use dark magic to try and claim what they think is rightfully theirs, leading to a battle of magic and loyalty within the Potter family and among Harry's friends.
Obviously, Harry, Ron, and Hermione would be key characters. They were at the center of the war and would likely continue to be important in the post - war era. They could be using their experiences to guide the wizarding world into a new era of peace and prosperity.
A new dark wizard or witch could be created specifically for this fanfiction. This character could be interested in using the Huntsman's skills for their own evil purposes. If the Huntsman refuses, they become enemies. This antagonist could have powers related to dark forest magic, something that the Huntsman is familiar with but in a more malevolent form.