One idea could be a crossover with the Naruto universe. Gohan as SSJ2 could end up in the Hidden Leaf Village and interact with the ninjas. Maybe he helps in a battle against a powerful enemy using his Saiyan powers.
You could start by establishing the setting and the situation. Say you choose a crossover with the Avatar: The Last Airbender world. Begin with Gohan SSJ2 sensing an unusual energy in that world and deciding to investigate. This sets the stage for the story to unfold.
The Phoenix Against the World was a fantasy novel written by Wang Yu. The novel was a fantasy world with reincarnation as the background, and the main character was a phoenix.
One common theme could be the struggle between Gohan's good nature and the newfound dark side. Maybe it involves his relationships being strained as his dark side emerges. For example, his relationship with his family and friends might change as he becomes more aggressive or unpredictable.
Gohan will most likely encounter other Z - fighters like Krillin and Tien. They were all part of the group back then. Also, there's a good chance he'll meet Master Roshi. Roshi was a key figure in Goku's training, so his interaction with Gohan could be really interesting. He might also come across Bulma, who was always involved in the Dragon Ball story, either by accident or because he needs her help with some time - related technology or something.
It can create new power dynamics. If Gohan has a dark side, it might make him a more unpredictable and potentially dangerous force in the universe. Enemies might see this as an opportunity to manipulate him or use his power for their own gain.
In this fanfiction, Gohan might change important events in the past. For example, he could prevent certain villains from getting stronger or save characters who died previously.
In 'bojack end story', it may represent the culmination of all the themes and plotlines that have been building up throughout the Bojack narrative. It could be a moment of reckoning for Bojack, where he has to deal with the consequences of his actions. It might also involve the fates of the other characters who are intertwined with his life. For instance, his friends, family, and colleagues. It could be a bittersweet ending that shows the complex nature of life and the choices we make.