One type of antagonist could be a corrupt Pokemon League official. In the fanfic, this official might bribe Ash to do something unethical, like throwing a battle against Iris. When Iris finds out, she'll feel betrayed. Another likely antagonist is a Pokemon hunter. If the hunter captures a Pokemon that Ash and Iris both care about, and Ash, in an attempt to rescue it, makes a deal with the hunter that seems to go against Iris's values, she'll feel betrayed. And sometimes, it could be a self - centered Pokemon trainer who wants to be the only star. They might set up Ash and Iris to fight each other and make it look like one has betrayed the other.
Another possibility is that it could be an old acquaintance who has changed for the worse. They might have been jealous of Ash and Lyra's success or popularity in the Pokémon world. This person could use their knowledge of Ash and Lyra's habits and weaknesses to betray them. It could also be a group of people rather than just an individual, like a team of thieves or poachers who see Ash and Lyra as obstacles to their illegal activities.
Gary could be a likely character. He has always been Ash's rival and there could be a plot where his jealousy or some other motive leads him to betray Ash. Another could be one of his so - called friends from the Pokemon League who might be influenced by power or some dark secret. Or, in some really dark fanfictions, it could be a Pokemon that Ash trusted deeply but for some reason turns on him.
Team Rocket is very likely. They've always been after Ash and his Pokémon. Using mind control on Ash would be a new way for them to get what they want. They could make Ash give them Pikachu or other strong Pokémon. Another one could be Giovanni. As the leader of Team Rocket, he has the resources and the motive to use mind control on Ash to further his own evil plans in the Pokémon world.
The main character is surely Ash. He is the one who is being betrayed. Mew is another important one. It might be that Mew is the cause, directly or indirectly, of Ash's betrayal. Then, Ash's Pokémon partners are likely to be main characters too. They might be confused or forced to side against Ash. And there could be some antagonists in the story, perhaps some evil trainers or organizations who are behind the plot to make Ash look bad and get betrayed.
Well, there could be an evil scientist in the fanfiction. This scientist might be researching the power of hypnosis on Pokemon trainers and sees Iris as a perfect test subject. They would use their advanced technology and knowledge of Pokemon behavior to hypnotize her. Also, a powerful psychic - type Pokemon that has gone rogue could be an antagonist. It might hypnotize Iris to do its bidding, like stealing other powerful Pokemon or causing chaos in Pokemon battles. And don't forget about a group of treasure hunters who want to use Iris's hypnotized state to find a hidden treasure that only she knows the location of through her adventures.
Even old enemies of the demigod world, who see Percy and Jason as threats, could be the antagonists. They might use deception and betrayal as a way to weaken the demigod forces, knowing that Percy and Jason are important figures among them.
In such fanfictions, a prevalent theme is broken trust. Ash and Iris could have been on a journey together when suddenly Ash meets someone new who convinces him to change his path, leaving Iris behind. This would make Iris feel betrayed. Another theme could be related to secrets. If Ash has been hiding something important about his Pokemon training methods from Iris, and she finds out in a bad way, it can create a sense of betrayal. Also, the theme of jealousy can come up. If Ash gets more attention or praise from other trainers for his Pokemon, Iris might feel left out and betrayed, thinking Ash doesn't care about her feelings or achievements.
Some fanfictions might have Misty betray Ash. Perhaps she gets lured by the promise of power or some valuable reward. She could be tricked into believing that Ash is no longer the friend she thought he was and that betraying him is for the greater good.
Well, sometimes the antagonist can be an internal struggle within Ash or May themselves. For example, Ash's over - ambition to become the best Pokémon trainer might lead him to make choices that seem like a betrayal to May. His single - minded focus on winning battles and collecting badges could make him neglect May's feelings. In this case, Ash's own ambition is acting as the antagonist in the story. Similarly, May's insecurities could make her misinterpret Ash's actions as betrayal, and her insecurities then become the antagonist in the relationship.
One possible main antagonist could be a powerful and arrogant trainer who wants to prove that he is better than Ash and Nora. He might try to steal their Pokemon or sabotage their battles.