In a fanfic about Ash and Iris betrayal, perhaps Iris could betray Ash over a powerful Pokémon they both encounter. Maybe she feels that Ash is not strong enough to handle it and decides to take it for herself, thinking it will help her on her journey to become a top Pokémon trainer.
Well, it could be that Iris is influenced by some other characters in the fanfic. They might convince her that Ash is holding her back in some way. So, she betrays him by leaving their group suddenly and joining forces with those who oppose Ash. This would create a lot of drama and tension in the story.
Another possibility is that there's a misunderstanding. Iris might see Ash doing something that she misinterprets as a betrayal of their friendship. In her anger, she then betrays him in return. For example, if Ash has to make a quick decision during a battle that seems to sacrifice Iris's Pokémon for the greater good, she could take it the wrong way and turn against him.
One possibility could be that in the fanfic, Diantha betrays Ash for power. Maybe there's a powerful organization that offers her something she can't resist, like control over all Pokémon battles in a certain region. She then uses Ash in some way to further her own goals, perhaps leading him into a dangerous situation that he wasn't aware of. This could lead to Ash feeling extremely hurt and betrayed, and it might cause him to question his own judgment in trusting people.
One possible scenario is that Greninja is tricked into believing that Ash is endangering its kind. So it decides to turn on Ash. Haruka, on the other hand, having known Ash for a long time, might try to convince Greninja of Ash's true nature. However, Greninja's loyalty is so shaken that it doesn't listen easily. In the end, Ash has to prove his worth and friendship to Greninja all over again.
Well, they could be betrayed by a new acquaintance in a strange town they visit during their travels. This new person could pretend to be friendly, but then steal their Pokemon or important items.
Well, it could be that Ash has finally had enough of Iris's overbearing behavior. Maybe she's been bossing him around about Pokemon training methods. So, Ash decides to stand up and tell her that he has his own way of doing things and that he's been successful with it. For example, Ash might have his own unique bond with Pikachu that doesn't follow Iris's ideas.
In general, Ash is often depicted as his adventurous and determined self. He might be shown as being a bit naive at times. Iris, on the other hand, is usually portrayed as strong - willed and feisty. However, it's important to note that spank fanfiction is not a typical or widely - accepted form of fanfiction and may contain elements that are not in line with the original characters' personalities in a more official sense.
Most likely, Iris could be seen as the main antagonist in this fanfic. Since the title says 'ash stands up to iris', it implies that Iris is the one causing some sort of problem that Ash needs to oppose. It could be her attitude or her actions that are creating conflict.
In a Pokemon fanfic where Ash trades Pokemon, a lot of interesting things can occur. He might trade a Pokemon that has been with him for a long time, like Pikachu. This could lead to a whole new adventure as he gets to know the new Pokemon he received. It could also change his battle strategies.
In the fanfic, Absol might be in some kind of trouble that Ash has to rescue it from. After that, Absol decides to join Ash's team. Ash would then have to train Absol and figure out how to best utilize its skills. They could go on adventures together, facing various challenges and meeting new Pokémon along the way. Absol could also introduce Ash to new areas or Pokémon that are related to its own origin or habitat.
Well, it's possible that Ash and Mewtwo team up in the fanfic. They could face a common enemy together. Mewtwo's incredible psychic powers combined with Ash's experience and determination would make them a formidable duo. And perhaps this encounter would change Ash's view on some things, like the true nature of Pokémon battles.
They might have an intense conversation about their past adventures. Maybe they'll share stories of the battles they've been in and the Pokémon they've caught.