His rival, Gary, could be a likely candidate. Gary has always been competitive with Ash, and in this fanfiction, his jealousy could reach a boiling point, causing him to betray Ash for his own gain, like trying to steal his Pokémon or get credit for his achievements.
Perhaps in this fanfiction, Ash is betrayed by a mentor figure. This person has been guiding him all along but has a hidden agenda. The rated m aspect could mean there are some intense battle scenes and moral dilemmas. Ash will have to reevaluate his beliefs and skills to overcome this betrayal and the challenges that come with it.
His rivals could be the ones to betray him. For example, Gary Oak might see Ash's godlike powers as a threat to his own status and decide to plot against him. Gary could spread false rumors about Ash to turn others against him.
In certain fanfictions, a Pokémon professor or an authority figure in the Pokémon world could betray Ash. They may have their own secret agendas. For example, a professor might use Ash's research data without his permission or manipulate him into dangerous situations for their own experiments. This would make Ash feel extremely betrayed as he looks up to these figures for guidance.
It could be a famous Pokémon trainer. Maybe someone who has traveled to many different regions and has a lot of knowledge about rare Pokémon.
Well, without actually reading the specific fanfiction, it could be about Ash Ketchum, who is in a 'godlike' state, being betrayed by someone. Maybe his friends turn against him due to jealousy of his newfound power. Or perhaps an enemy manages to deceive those close to him, making them think Ash has done something wrong when he hasn't.
Maybe a new, mysterious villain who has a grudge against Ash or wants to use his skills for their own evil purposes. This villain might be from a far - off region and has special powers that allow them to hypnotize people. They see Ash as a useful tool to carry out their plans in the Pokémon world.
One common theme could be Ash being betrayed by his friends in the Pokémon world. For example, they might leave him for a more powerful trainer or because of a misunderstanding. Another theme could be betrayal by the Pokémon League, like being wrongly disqualified from a major tournament. Also, some fanfictions may explore Ash being betrayed by a new character who has ulterior motives and tries to undermine his journey.
Ash could become more confident and wise as a Dragon Master. His decision - making skills would improve as he deals with powerful and often unpredictable dragon Pokémon.
One possible plot could be that Ash, being from a different world, is initially welcomed into the RWBY universe. But then, he might be betrayed when his Pokémon powers are seen as a threat. Maybe the RWBY characters fear that his abilities could disrupt the balance of their world. For example, if his Pikachu's electricity causes unexpected power surges in a world that has its own unique energy sources like Dust.
It could be Gary. Gary has always been a rival to Ash. Maybe in this fanfiction, Gary gets jealous of Ash's progress and decides to betray him by making false accusations to the Pokemon League about Ash using illegal training methods.