In some fanfictions, Ash might become evil after heartbreak by losing his faith in the goodness of the world. For example, if a character he deeply trusted betrays him, he could start to view relationships as tools for power or revenge. This new mindset might lead him to make choices that are considered evil, like using underhanded tactics to defeat opponents or turning a blind eye to the suffering of others.
One common sign is a change in his attitude towards friends. He may become more distant and cold, not showing the same warmth and loyalty as before. Another sign could be his new approach to battles. Instead of fighting fair, he might start using dirty tricks. For example, in a Pokémon battle, he could intentionally harm the opposing Pokémon more severely than necessary.
One popular 'ash becomes evil after betrayal fanfiction' is 'Ash's Dark Descent' which explores how Ash's trust is shattered and he turns to the dark side. It has some really intense scenes where you can see his transformation.
Gary could be the main antagonist. He has always been Ash's rival and seeing Ash turn evil, he might feel responsible to stop him. Gary could gather his own team of powerful Pokémon and use his wits to oppose Ash at every turn.
One possible plotline could be that Ash is betrayed by his friends. This heartbreak and sense of abandonment turns him evil. He then starts using his Pokémon in cruel ways to seek revenge on those who wronged him.
The following are some recommendations for novels that break the heart: " The Cold Palace's Prisoner,"" The Heartless Ugly Husband Is Going Against the Sky,"" Burning Love: Escape from Satan's CEO,"" Red Dust Roars at the West Window,"" Doomsday Cannon Fodder,"" Just Like Your Gentle Landing Point-Complete Version,"" Intoxicated,"" Beware of That Vampire,"" I Dumped the Male Lead After Wearing a Sadistic Text,"" Phoenix: The Cold Palace,"" The Legend of the City Fallen Out of Love,"" Rebirth After Poison: Di Daughter Feng Hua, Li Shang's Soul Flower Calamity, Abandoned Concubine and Absolute Love, Devil Baby Mistaken Father, Empress Han Shu, Soak in the Bubble, If I'm Deep in Love with You, It's Not Too Late.
Gary could also be the one to cause Ash's heartbreak. Maybe Gary outshines Ash in a big Pokemon battle and then mocks him for it. This could make Ash feel like a failure and break his heart. Gary has always been a bit of a rival to Ash, so this kind of situation is plausible in fanfiction.
In some fanfictions, Ash might become evil after betrayal when his trust is shattered. For example, if his friends turn on him for some false accusations, he could start to see the world in a different, more cynical way. This broken trust might lead him to believe that power is the only thing that matters, and he starts to pursue it without regard for the consequences, gradually turning evil.
A new, powerful villain could be the cause. This villain might target Ash's Pokémon and manage to steal them all away. Ash would be heartbroken not only because he lost his Pokémon but also because he feels he has failed to protect them.