I'm not sure if there are extremely popular ones specifically with this plot. However, in the vast world of fanfiction, there might be some that have gained a bit of a following among a niche group of Pokémon fans who are interested in darker and more alternative storylines.
Well, a 'May kills Ash' fanfiction might involve a plot twist where May has been brainwashed by a villain. She could be made to believe that Ash is a threat to the world they live in, and so she takes it upon herself to eliminate him. This could lead to a very intense and emotional story as their friends try to figure out what happened and stop May.
I haven't come across a 'pikachu kills ash fanfiction' myself. But in the world of fanfiction, people sometimes create very extreme and unexpected scenarios. If such a fanfiction exists, it may be written by someone who wants to explore the darker side of the Pokémon universe or perhaps is trying to make a statement about the relationship between Pikachu and Ash. It might shock and intrigue readers who are used to the positive and heroic portrayals of the characters in the official Pokémon media.
One possible fanfiction could be about Ash's adventures in Hoenn during the month of May. Maybe he discovers a new Pokémon species that is only active during this time of the year. He could be traveling with his usual companions and facing challenges specific to the Hoenn region.
It could be a rival trainer. Rival trainers are often very competitive in the Pokémon world. Maybe this rival is jealous of Ash and May's progress and decides to betray them to slow them down. They might spread false rumors about Ash and May, causing other trainers to be distrustful of them.
Often, these fanfictions will take the characters out of their normal settings. For example, they might end up in a different time period or a strange new land. This allows for a lot of creativity in the storylines. And the character development of May and Ash is usually a big part of it, showing how they grow and change throughout the story.
Yes, there might be. Fanfiction covers a wide range of scenarios and relationships, so it's possible that someone has written a story where May cheats on Ash. You can try searching on popular fanfiction websites.
A possible fanfiction plot could be that Ash, Serena, and May are invited to a mysterious island full of unknown Pokemon. They have to work together to survive and discover the secrets of the island. Ash's leadership, Serena's ability to communicate with Pokemon, and May's quick decision - making skills would be crucial.
One way is to focus on their friendship. For example, write about how they support each other during Pokémon battles. They can exchange tips on training Pokémon or strategies for winning competitions.
Ash could get angry. He has a strong sense of justice, and he might feel that May has violated their friendship. He could challenge her, not in a violent way, but more in a way to get an explanation and to try to make her see the error of her ways. He would likely be determined to show her that what she did was wrong.