Another possibility is that a new character emerges who seems more suitable for the role. This new character could have some special abilities or a stronger connection to the prophecy. As a result, Ash is deemed no longer the Chosen One.
It might also be due to a betrayal. Suppose someone close to Ash, like a trusted ally, turns against him and reveals some secret that makes others question his worthiness as the Chosen One. This could lead to his title being stripped in the fanfiction world.
One reason could be that he fails a major quest. For example, if there's a prophecy that he must defeat a certain powerful villain to maintain his 'Chosen One' status and he doesn't succeed. Maybe the villain was too strong or Ash made a crucial mistake during the battle.
He could be very depressed at first. Losing such an important title that he may have worked hard for or believed in for a long time can be a huge blow to his self - esteem.
Perhaps in the fanfiction, Ash was betrayed by a powerful mentor figure. This mentor, who was supposed to guide him, saw Ash as a threat to their own power or plans. So they leaked Ash's secrets to his enemies, which led to his downfall. It could also involve a love interest. Say, a girl Ash trusted and liked turned out to be working for the villains all along and used his feelings for her to betray him.
One reason could be false accusations. Maybe someone spread rumors about him being involved in dark magic again, even if he was innocent. In the cut - throat world of Hogwarts politics in fanfiction, such false accusations could cost him his job.
His rival could be the one to betray him. Rivals are often jealous and competitive. If Ash's rival saw an opportunity to gain an advantage by betraying him, they might do it. For instance, they could lie about Ash to the Pokémon League, getting him disqualified from important battles.
One reason could be a power struggle. If there was a rare and powerful Pokémon at stake, Ash might be tempted to betray Korrina to get it for himself. In the Pokémon world, power and rare Pokémon are highly coveted.
Another reason might be related to Pikachu's own growth. As Pikachu becomes more powerful and self - aware, it might feel that it needs to go on its own journey without Ash. It could be seeking new challenges and experiences that it believes Ash can't provide, like exploring regions that Ash has no intention of going to or training with Pokémon of a different caliber.
One reason could be a powerful magic spell cast on him by a villain. For example, a sorcerer who wants to stop Spider - Man from interfering in his evil plans might use a spell that disrupts the source of his powers. Another possibility is that he gets exposed to some sort of radiation or chemical that nullifies the mutation that gives him his powers. Maybe he enters a new dimension where the laws of physics are different and his powers don't work there.
Neville could be a likely candidate. He had the courage and the connection to the prophecy as well.
One possible reason could be jealousy. Maybe his friends are jealous of Ash's success in his Pokemon journey. For example, if Ash wins a big tournament and gets all the fame, his friends might feel left out and betrayed. Another reason could be a misunderstanding. Ash might do something that his friends misinterpret. Say he makes a deal with an enemy in order to save his Pokemon, but his friends don't understand the situation and think he's turned on them.
Another reason could be her relationships. If she has a fight with a friend or a love interest. Let's say she and Edward had an argument over his over - protectiveness. That could easily make her lose her cool.