It could be a fellow student who was secretly jealous of Harry all along. Maybe someone like Draco Malfoy. He had always been at odds with Harry and in a fanfiction, he could be pushed to the point of betraying Harry for his own self - centered reasons. Another possibility is a teacher. A teacher who was influenced by the dark side or had some hidden agenda could betray Harry. For example, if there was a teacher who was secretly working for Voldemort or a new dark wizard.
It's also possible that one of Harry's closest friends could be the betrayer. In some dark and twisted fanfictions, the idea of a friend turning on Harry can add a lot of drama. For instance, Ron could be written as the betrayer. Maybe he got tired of living in Harry's shadow or was influenced by some external force that made him turn against Harry. This would be a huge shock to readers as Ron was always seen as a loyal friend in the original series.
The Ministry of Magic officials could be the betrayers. In the original story, the Ministry was often corrupt and slow to act against real threats. In a fanfiction, some high - ranking officials might see Harry as a liability rather than an asset. They could be afraid that Harry's actions would expose their own inefficiencies or wrongdoings. So, they might betray him and leave him for dead to save their own skins.
It could be some of the pure - blood supremacists who were biding their time. Even though the war was over, they might still resent Harry for his role in defeating Voldemort and decide to get revenge by making it look like he betrayed them. Another possibility is some of the Ministry officials who were corrupt and didn't want Harry's influence around.
A possible betrayer could be a jealous demigod. There are always those in the Percy Jackson world who envy Percy's abilities and the attention he gets. This demigod might see an opportunity to get rid of Percy and make themselves look better in the eyes of the other campers.
Another possibility is that it could be an old acquaintance who has changed for the worse. They might have been jealous of Ash and Lyra's success or popularity in the Pokémon world. This person could use their knowledge of Ash and Lyra's habits and weaknesses to betray them. It could also be a group of people rather than just an individual, like a team of thieves or poachers who see Ash and Lyra as obstacles to their illegal activities.
A jealous rival could be a likely betrayer. Maybe someone who is envious of Bell's popularity or his relationship with certain characters. For example, another adventurer who feels overshadowed by Bell might betray him to gain an advantage. Another possibility is a character who is being manipulated by a darker force. They might not have wanted to betray Bell originally but are forced to under the influence of some evil power.
Gary Oak could be a likely betrayer. He has always been Ash's rival, and in some fanfiction, he might take things too far and betray Ash in a crucial Pokémon battle, like using underhanded tactics to win. This would surely make Ash cry.
It could be Dumbledore. He always had his own plans and secrets. Maybe Harry discovers that Dumbledore was using him all along for some greater purpose that involved sacrificing Harry's well - being. Another likely betrayer could be Ron. Ron had moments of jealousy in the original story. In this fanfiction, his jealousy could have grown to the point where he turned on Harry for his own gain or out of envy.
Another type of betrayer could be a family member. In some fanfictions, family dynamics can be complex. A family member might betray fem Percy out of a sense of duty to a different cause or because they believe she is a threat to the family's reputation or safety.
The Ministry of Magic could also be the main antagonist in this case. If the Ministry is corrupted or under the influence of dark forces, they could manipulate Harry's friends. They might convince his friends that Harry is a danger to the wizarding world order, and his friends, being naive or misinformed, end up betraying him.
Iruka Sensei could also be a candidate. He was one of Naruto's first supporters and has a deep connection with him. He would probably risk a lot to save Naruto.
Perhaps there was a dark secret about Naruto's origin that was revealed in a way that made others fear him. For example, if it was discovered that he had some connection to a feared enemy or an ancient evil. This could lead to his betrayal as people's fear overrode their previous loyalty to him. Also, jealousy among his peers could be a factor. If Naruto was constantly getting stronger and more popular, some might have become envious and were easily convinced to turn against him.