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.
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 the manga, Gohan never managed to defeat Goku. Their battles often ended with Goku coming out on top or the fight being interrupted for some reason.
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.
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.
In a Naruto - Goku fusion, there could be a new form of energy manipulation. Goku manipulates ki, and Naruto uses chakra. They might create a hybrid energy that has the best of both worlds. This energy could be used for long - range attacks like Goku's energy blasts and also for close - combat like Naruto's Rasengan. Also, the fusion could have enhanced senses, borrowing from Goku's Saiyan senses and Naruto's ninja training.
Well, it could be super powerful. The fusion might have Goku's Saiyan strength and ability to transform into Super Saiyan forms, combined with Naruto's ninja skills and chakra control. It could fly around with the speed of a Saiyan and use Rasengan - like attacks with the power of a Kamehameha. Just imagine a character with the orange gi and a headband.
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.