One idea could be that Frieza, in a strange turn of events, spares Yamcha during a battle and then gradually becomes intrigued by his tenacity. This leads to them forming an unlikely alliance against a common enemy. As they spend more time together, they start to understand each other's motives and personalities, and a unique bond forms between them.
One possible plot could be that Yamcha, known for his tenacity, somehow ends up in a situation where he has to team up with Frieza. Maybe they are both forced to face a common enemy that is even more powerful than Frieza at his peak. This could lead to an interesting dynamic as Yamcha tries to get Frieza to work as a team, while Frieza is his usual self - conniving and power - hungry. Their interactions would be full of tension and mistrust at first, but over time, they might develop an odd sort of respect for each other.
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.
One idea could be that Frieza, after being resurrected yet again, finds himself in a situation where he has to team up with Gohan. During their time together, they start to understand each other's motives and past traumas. Gohan's kindness and sense of justice gradually influence Frieza in unexpected ways.
Perhaps a fanfic could be about an alternate universe where Yamcha was always more confident in his relationship with Bulma. In this universe, they go on adventures together, exploring new planets and having to rely on each other. This would strengthen their bond and make for an exciting story about their relationship.
One idea could be that Frieza and Cell team up to take over the universe in a new and unexpected way. They combine their powers and intelligence to outwit all the other powerful beings.
One idea could be that Frieza and Goku are forced to team up against a new, even more powerful enemy. They start off hating each other but gradually learn to respect each other's skills.
A plot could involve a love triangle where Female Frieza has feelings for Goku, but Goku is oblivious and focused on his own goals. Meanwhile, another character is also interested in Goku. This could lead to a lot of comical and tense situations. Or perhaps Female Frieza challenges Goku to a series of contests not related to fighting, like cooking or dancing, to prove she can be better than him in other areas.
Maybe Yamcha gets a special gaming device that gives him unique powers in the real world, but only when he completes certain in - game quests. So he has to balance his normal life as a Z - Fighter with his new gaming - related adventures. For example, he might need to defeat a powerful in - game boss to gain the power to heal his wounds faster in real battles.
One idea could be Yamcha getting a new power-up. Maybe he discovers a hidden technique during his training in the wastelands. He could then use this new power to face off against an old enemy, like the Saibamen. This would show his growth as a character.
One idea could be that Frieza somehow ends up in the wizarding world. Maybe he's initially interested in the powerful magic there to increase his own strength. He could try to take over Hogwarts, thinking it's a place full of valuable secrets. Another idea is that Harry Potter and his friends discover a way to travel to Frieza's universe and they have to use their magic to survive and find a way back home. Or perhaps Frieza is magically transformed into a Hogwarts student and has to deal with the rules and social life at the school while still having his evil tendencies.