Often in these fanfictions, Ash's change to evil is gradual. He might start by making small, unethical decisions in battles, like using underhanded tactics. As he goes further down this path, he begins to target his old friends. He could also try to take over the regions one by one, using his Pokemon's strength to subdue other trainers and Gym Leaders. This creates a lot of conflict as his friends and former allies try to stop him.
One common plot is that Ash gets betrayed by someone he trusts deeply, which causes him to turn evil. For example, if the Pokemon League rejects him unfairly. Another plot could be that he gets influenced by a powerful, evil Pokemon or a dark force. He might then start to use his Pokemon in cruel battles, not caring about their well - being.
One common theme is the struggle for identity. When Ash is turned into a Pokemon, he has to re - evaluate who he is. Another theme is the power struggle against Team Plasma. Ash often has to find a way to break free from their control. And of course, there's the theme of friendship. His Pokemon friends usually try to help him in his new form.
In a Pokemon Ash turns evil fanfiction, he might start using his Pokemon for wrong purposes. For example, instead of battling for sport and friendship, he could use them to steal from other trainers or take over Pokemon Centers. His Pikachu, usually so loyal, might be conflicted about following his new, evil ways.
One exciting plot could be Ash getting a special Beyblade that has powers related to Pokemon. For example, it might be able to call upon the strength of Pikachu's electricity to boost its spin. Another plot could involve Ash traveling to a world where Pokemon and Beyblade battles are combined, and he has to learn new strategies to compete. A third plot might be that Ash discovers a rare Pokemon that can transform into a Beyblade, and he has to protect it from villains who want to use its power for evil.
One common plot could be Ash getting injured during a tough Pokemon battle. For example, when facing a powerful and rare Pokemon like Mewtwo. His Pikachu might try its best to protect him but Ash still gets hurt. Another plot could involve Ash getting injured while exploring a new and dangerous area in the Pokemon world, like an uncharted forest filled with wild and aggressive Pokemon. Maybe he stumbles upon a hidden lair of a group of Team Rocket - like villains who attack him.
One common plot is Red coming back to save the Pokemon world from a new threat. This could be a powerful and evil organization that has emerged while he was away.
One interesting plot could be that Ash discovers a secret power within Mew that can help him defeat a powerful new villain in the Pokemon world. Mew might choose Ash as its special trainer to unlock this power.
One common plot is when a villain tries to mind control Ash to use him against his friends. For example, Team Rocket might get their hands on a new device that can control Ash's mind. Then they could make him battle his own Pokémon against other trainers in a cruel way. Another plot could be an evil Pokémon with mind - control abilities targeting Ash. This Pokémon might be under the control of a more powerful and mysterious force.
Another plot is that Ash dresses as a girl as part of a bet or a challenge. Throughout the fanfiction, he discovers new aspects of himself or the Pokemon world that he wouldn't have otherwise. For example, he might learn about the unique challenges female trainers face.
One interesting plot could be a trainer who turns into a Pikachu and has to navigate the Pokemon world from a different perspective. They might struggle with their new small size and electric abilities at first, but then learn to use them to their advantage in battles.
Obviously, Ash is a central character. Pikachu is also often there, as it's Ash's main Pokemon. Misty and Brock might be in the fanfiction too, trying to figure out what has happened to Ash and how to stop his evil ways. Sometimes, Gary Oak could be involved, either as an antagonist to Ash's new evil self or as someone trying to help bring him back to the good side.