The main antagonist could be a mysterious figure who has some kind of hold over Ash's mom. This figure might be blackmailing her into betraying Ash. He could be an evil Pokémon collector who wants Ash's Pokémon for his collection. He uses Ash's mom to get close to Ash and then tries to take what he wants. Ash would not only have to deal with his mom's betrayal but also this new and dangerous threat.
If his mom betrays Ash, it's possible that there are other family members or old friends who support his mom's actions. They could become antagonists as well. Maybe an uncle who has always been jealous of Ash's potential and sees this as an opportunity to get rid of him. Or a family friend who has some hidden motives and helps his mom in the betrayal. These characters would then be obstacles for Ash as he tries to overcome the betrayal and move forward.
One possible plot could be that his mom reveals she has been working with an evil organization all along. She hands Ash over to them for some dark purpose, like using his unique Pokémon connection for their evil experiments. Ash would feel extremely hurt and betrayed, having to then find a way to escape and also come to terms with his mother's true nature.
It could be a new character, someone who has a long - standing grudge against Ash's group. This character might manipulate Ash into betraying his friends by preying on his insecurities or desires.
It could be a powerful Pokemon trainer who is jealous of Ash's connection with Serena's mom. This trainer might try to disrupt their relationship and stop Ash from getting any help or knowledge from her.
Obviously, Ash and his mom are the main characters. Ash is usually depicted as a young and curious character, full of energy. His mom, on the other hand, is often portrayed as a loving and supportive figure in his life.
Ash, who is the well - known Pokémon trainer, and his mom. Ash has all his Pokémon with him, but his mom is the new addition to his travel companions. She might bring a different perspective to their adventures compared to Ash's usual friends.
It could be the one who manipulated Grayfia into betraying Naruto. Maybe it's a powerful and cunning villain from Naruto's world or even from another dimension. This antagonist could have a hidden agenda that involves getting rid of Naruto by using Grayfia.
It could be a new powerful monster that was sent after Percy because his mom was no longer there to protect him. Maybe a monster that has a grudge against Percy's family.
It could be a new and powerful trainer who manipulates Anabel into betraying Ash. This trainer might be jealous of Ash's success and see Anabel as a means to bring Ash down.
A powerful and envious Pokémon trainer could be the main antagonist. This trainer might be jealous of Ash's bond with Greninja and decides to break it. He could use dark magic or some sort of mind - controlling device to make Greninja turn against Ash.
It could be a new character who is jealous of Ash and Skyla's friendship. This character might spread false rumors about Ash to Skyla, causing her to feel betrayed. So, this new jealous character would be the main antagonist.