One possible plotline could be Ash's intense final battles in the Hoenn League. He might face off against his toughest rivals, using strategies he's developed throughout his journey in Hoenn. For example, he could use his Pikachu's new electric moves combined with the teamwork of his other Pokémon like Sceptile and Swellow to outwit his opponents.
One of his toughest opponents could be Tyson. Tyson was a very strong trainer in the Hoenn League in the original series. His Pokémon were well - trained and had unique battle strategies. Ash would have to really bring his A - game to defeat him.
His Pikachu might gain more control over its electric powers. For instance, it could learn to direct its thunderbolts with more precision, hitting the opponents' weak points accurately. This evolution in Pikachu's skills could be due to the intense battles in the Hoenn league.
In the 'Ash Wins Hoenn League' fanfic, it could be that Ash has some unexpected help. Perhaps he teams up with some local trainers in Hoenn who have unique skills or Pokémon that assist him in the league. They might share their knowledge of the local Pokémon and terrain, which gives Ash an advantage in the battles.
A trainer with a rare and powerful Legendary Pokémon could also be a tough opponent for Ash. In the Hoenn region, there are Legendary Pokémon like Groudon or Kyogre. If a trainer has managed to form a bond with one of them, it would be extremely difficult for Ash to defeat them.
One idea could be that Ash's victory in the Alola League is due to his strong bond with his Pokémon. His Pikachu, for example, could have evolved a new move during the final battle that gave them the edge. Another idea is that Ash's experience from all his previous regions finally culminates in this victory, and he uses strategies he learned along the way.
In the Unova League in the Pokemon series, Ash winning is quite an exciting concept in fanfiction. It shows his growth as a trainer. Maybe in this fanfiction, he finally overcame all his opponents with his strong team, strategic thinking and unwavering determination.
Gary could also be important. Maybe in this fanfiction, Gary is a rival that Ash has to outwit and defeat in a more intense way compared to the original story. Their rivalry could be a major driving force for Ash's growth and success in the league.
Perhaps he defeats some of the Elite Four members who are participating in the league. They are known for their strength, so it would be a huge accomplishment. And of course, any recurring rivals from his past adventures like Trip or Paul.
In an 'Ash Wins Kalos League' fanfiction, one possible plot could be that Ash finally masters his Mega Evolution techniques better than ever. He has a series of intense battles where he outsmarts his opponents. His bond with his Pokémon, especially Greninja, reaches new heights. They use their unique moves in creative ways to defeat strong adversaries and claim the victory in the Kalos League.