Jiren could still be a tough opponent in the 'vegito tournament of power fanfiction'. His power level is extremely high, and he has great combat skills. Even for Vegito, defeating Jiren would be no easy feat as Jiren has proven his strength time and again in the original tournament.
It's really hard to say. Vegito has the combined power of Goku and Vegeta, which is incredibly strong. But Kefla is the fusion of Kale and Caulifla, also very powerful. It could depend on the situation in the fanfiction, like if one has a power - up during the fight.
In vegito crossover fanfiction, characters like Jiren would be great. His strength and stoic nature would make for some intense interactions with Vegito. Also, Android 18 could be included. She has her own unique set of powers and a strong will. Her presence could add some interesting dynamics, especially if she has to team up with Vegito against a common enemy. And don't forget Frieza. His evil nature and thirst for power always make for an exciting addition to any Dragon Ball - related story.
In Ultra Man Story, Ultraman is the central figure. Besides him, there are often human characters. These human characters play important roles, sometimes as scientists who study the monsters or Ultraman, and other times as soldiers or ordinary people who get caught up in the battles and try to help Ultraman in their own ways.
It could be Frieza. He might be jealous of Vegito's power and decides to target Bulma to get to Vegito. His actions could make Bulma realize the danger she's in because of her association with Vegito, leading her to give up on him.
In crossover fanfiction, Vegito Blue often brings a powerful and exciting element. His character combines the strengths of Goku and Vegeta in a unique way. For example, his combat skills and strategic thinking are enhanced due to the fusion. Writers can use him to create epic battles against various foes from different fictional universes.
One aspect of Vegito and Female Gogeta fanfiction could be the exploration of their unique power combinations. In these fanfictions, writers might create scenarios where they team up against a powerful enemy. For example, they could face a new, extremely strong villain that neither could defeat alone. Their combined strength and different fighting styles would make for an exciting story.