It could be that an external force, like a dark wizard in disguise, is the main antagonist. This dark wizard targets Hermione because of her potential to be a great threat to their evil plans. They use magic to cloud the minds of her friends, making them believe Hermione is up to no good. The friends, being under this spell, betray Hermione without realizing they are being manipulated. The dark wizard then watches as Hermione struggles with this betrayal, all part of their grand scheme.
Hermione's friends themselves could be seen as the antagonists in a sense. If they let envy or petty grudges overshadow their friendship, they are causing harm to Hermione. For example, if they feel overshadowed by Hermione's achievements and decide to ostracize her, they become the source of her pain and betrayal. They might not be traditional 'evil' antagonists, but their actions are what drive the conflict in the fanfiction.
It could be an outsider who manipulates Twilight's friends. This character might be envious of Twilight's popularity or power in the magical realm. They trick Twilight's friends into believing false things about her, making the friends turn against her.
One possible plot could be that Hermione's friends start believing false rumors about her. For example, they might think she's been stealing potions ingredients for personal gain when in fact she was framed. As a result, they shun her and exclude her from their group activities. This makes Hermione feel isolated and betrayed, and she has to find a way to clear her name and either regain her friends' trust or find new allies.
It could be a new character introduced in the fanfiction. Maybe someone who has infiltrated the Order and wants to create chaos by turning them against Hermione. This person could be a spy from the Death Eaters or another dark - aligned group, with the goal of weakening the Order from within by making them lose one of their most intelligent and powerful members.
The Ministry of Magic could also be the main antagonist in this case. If the Ministry is corrupted or under the influence of dark forces, they could manipulate Harry's friends. They might convince his friends that Harry is a danger to the wizarding world order, and his friends, being naive or misinformed, end up betraying him.
One possible reason could be jealousy. Maybe her friends are envious of Hermione's intelligence and magical abilities. In a fanfiction, this could lead them to betray her to gain an advantage or to make themselves look better. Another reason might be a misunderstanding. A miscommunication or false assumption could cause her friends to turn against her.
It might be a rogue ninja from the Wave. They could have a vendetta against Konoha and see Naruto as an easy target to frame and cause chaos between the two places.
A new, original villain could also be the main antagonist. This villain could be someone from Percy's past who has a grudge against him and wants to use the Avengers as a way to get revenge. By making Percy betray the Avengers, this villain can not only harm Percy but also cause chaos among the powerful superhero group.
Maybe there is an evil Pokemon trainer who has influenced Ashley to betray Ash. In this case, that trainer would be the main antagonist. He or she might have promised Ashley something in return for her betrayal, like rare Pokemon or power.
Obviously, Kami would be the main antagonist. Since the title says 'naruto betrayed by kami', Kami is the one doing the betraying, which makes him the bad guy in this fanfiction.
It could be a new and powerful trainer who manipulates Anabel into betraying Ash. This trainer might be jealous of Ash's success and see Anabel as a means to bring Ash down.