In the 'goku and gohan betrayed fanfiction', perhaps they are betrayed due to a misunderstanding. Say, Goku makes a deal with an unknown force to save the universe, but it's misconstrued as him allying with the enemy. Gohan, being associated with Goku, is also seen as a traitor. And this misunderstanding could be spread by a character with their own motives, like a power - hungry individual who wants to take over the Z - fighters' leadership.
It could be Vegeta. Maybe in this fanfiction, his pride gets the better of him and he feels overshadowed by Goku and Gohan's power. So he fabricates some lies to make them look like traitors to the rest of the group.
In some fanfictions, Gohan and Goku might have a series of conversations that open up new levels of understanding between them. Gohan could share his thoughts and feelings about his life and future, and Goku would listen and offer his own insights. This kind of communication can really strengthen their bond.
In such fanfictions, Goku might develop by becoming more of a mentor to Gohan. He could teach Gohan new fighting moves and also how to control his emotions better during battles.
One possible interaction is that Bardock could spar with Goku and Gohan. He'd test their limits and see how much they've learned about fighting. Another could be Bardock sharing stories of Planet Vegeta with them, which would be really interesting for Goku and Gohan to hear.
In many fanfictions, Goku's protectiveness of Gohan is shown through his constant presence. He might train Gohan more rigorously to make him stronger so he can defend himself. For example, in some stories, Goku takes Gohan to special training grounds that are hidden from the rest of the world. This not only protects Gohan from potential threats during the training but also hones his skills in a more secluded environment.
In a fanfiction where Future Gohan meets Goku, it could be an emotional reunion. Gohan might be filled with a sense of relief and joy, seeing his father again. He could show Goku all the things he's been through in the future, and Goku would be both proud and sad about what his son has endured.
One of the characters who could betray Goku is Piccolo. Although they've been allies for a long time, in fanfiction, things can change. Perhaps an ancient evil force takes control of Piccolo's mind and makes him turn on Goku. Or it could be Krillin. He might be influenced by an outside force that convinces him Goku is becoming too dangerous. Also, don't forget about the Kais. If there's some sort of power imbalance or a threat they perceive from Goku, they might betray him to maintain the order of the universe in the fanfiction.
In a Gohan x Goku fanfic, their relationship can be delved into by creating scenarios where they have to rely on each other completely. For example, if they are in a situation where Goku's strength and Gohan's intelligence are both required to escape. Their different personalities can also be highlighted. Goku's carefree nature contrasted with Gohan's more studious and responsible side. And of course, flashbacks to Gohan's childhood and how Goku's presence or absence affected him can add depth to their relationship.
You can focus on their emotional bond. For example, show how Goku's pride in Gohan's growth and achievements affects their relationship. It could be about Gohan seeking Goku's approval and Goku being there to give it wholeheartedly.