In fanfiction, Gary could be a likely character to betray Ash. He has always been a rival and might have ulterior motives. For Dawn, Zoey could potentially betray her. Zoey has been a tough competitor and might be jealous enough to take some underhanded actions. Another possible betrayer for Ash could be Team Rocket. They've been after his Pikachu for a long time and could use betrayal as a new tactic. For Dawn, perhaps a new coordinator who is envious of her popularity in the coordinator world.
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.
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.
Gary Oak is a likely character. He has always been a rival to Ash and in fanfiction, he might betray Ash out of jealousy or a desire to be the ultimate Pokémon trainer. Another could be Misty. Maybe she gets influenced by some external force or her own insecurities and turns against Ash. Brock could also be a candidate in some stories. If he falls in love with a girl who has a vendetta against Ash, he might be forced to choose between his loyalty to Ash and his new love interest.
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.
One likely character could be a rival trainer. They might see Fem Ash as a threat and betray her to get an edge in competitions. Another could be a so - called friend who is jealous of Fem Ash's success.
Their closest friends like Brock and Misty would surely be affected. They've been through so much with Ash, and his betrayal would be a huge shock. And for Lyra, her friends in her own region might be deeply hurt.
Rias could be a character who betrays Issei in some fanfictions. If she were to face a difficult decision between protecting her family's reputation and standing by Issei, she might choose the former. Another possibility is Akeno. If she were to be influenced by some ancient evil power that made her turn on her friends, Issei could be a target.
Natsu could be a character who betrays Lucy in some fanfictions. Maybe he gets influenced by some dark magic that makes him turn on her. Gray is also a possibility. He might be jealous of Lucy's growing power or popularity in the guild and decides to betray her for his own gain.
Vegeta could be a likely character. In some fanfictions, his pride and envy of Goku's strength might lead him to betray Goku. He might think that by getting rid of Goku, he can become the strongest in the universe. Another one could be Frieza. Even if he pretends to be an ally in some alternate storylines, he could betray Goku at a crucial moment to regain his power and dominance. Also, a new and powerful character introduced in the fanfiction, who is envious of Goku's popularity and power, could easily be a betrayer.
There's a chance that Scar could betray Edward in certain fanfiction concepts. Scar has his own motives and a complex past. If he feels that Edward is getting in the way of his revenge or his understanding of alchemy, he might betray him. Additionally, some fanfictions might explore the idea of an old acquaintance from Edward's childhood betraying him. Maybe someone who was once a friend but has since been corrupted by power or a dark influence. And then there's always the possibility of a new, mysterious character being introduced specifically to betray Edward for some yet - to - be - revealed reason.