For Yamcha, you can focus on his growth from being a bit of a comical character to a more serious and respected fighter in the context of his relationship with Frieza. Maybe he learns from Frieza's cold and calculating nature how to better strategize in battles. For Frieza, his development could be about him learning to care for someone other than himself. He could start to see Yamcha as an equal, which is a huge shift from his usual superiority complex.
You can also make him have a unique role in the story. For instance, he could be the one to discover a new threat to the Earth before anyone else. He then has to convince the other Z - Fighters to take this threat seriously. This would put him in a leadership position and make him stand out more.
Maybe it's a completely new and unknown kami. A kami created specifically for this fanfiction. This kami could have unique powers and a different view of the ninja world compared to the existing characters in Naruto. It would add a fresh and exciting element to the story.
Maybe it's an existing character from Naruto who has been elevated to Kami status. For example, Tsunade could be turned into a Kami, and Naruto's relationship with her could be a very different dynamic from their previous ninja - leader relationship. Or it could be Kaguya, who was already a very powerful being, and in this fanfiction, she reforms and becomes a Kami and Naruto's wife.
No. Abuse is never an appropriate topic, especially when it involves beloved characters from a popular series like Dragon Ball. It goes against the positive values that the series usually promotes.
In fanfiction, the 'kami' could be an original deity created by the author. This new 'kami' could have its own motives and reasons for giving a gift to Naruto. Maybe it's a kami that has been observing Naruto's journey and decides to interfere to help him achieve a greater purpose. It could be a kami associated with nature, like a kami of the wind or the fire, and the gift could be related to that element.
Perhaps it could be a female version of an existing kami from Naruto lore. For instance, a female counterpart of the Sage of Six Paths. She would have vast knowledge and power, and her training of Naruto would be a way to pass on that ancient wisdom and strength.
A popular Yamcha fanfiction is 'Yamcha's New Beginnings'. In this one, Yamcha decides to start anew after feeling left behind by his friends. He goes on a solo adventure, meets new allies and enemies, and in the process, he redefines himself and his place in the Dragon Ball universe. It gives a fresh perspective on his character.
Interesting strong Yamcha fanfics often give him new relationships or character dynamics. Like he could form an unexpected alliance with a former enemy, and through that, his character develops in new and exciting ways. Also, if the fanfic delves deeper into his backstory and uses that to fuel his new - found strength, it can be really engaging.