One possible plotline could be that Broly, in his rage, accidentally provokes Beerus. Broly, not knowing who Beerus is, attacks him. Beerus, initially amused, decides to teach Broly a lesson but soon realizes that Broly's power is growing at an alarming rate. This leads to an intense battle where Broly pushes Beerus to use his full power. Another plotline could be that Beerus hears about Broly's power and decides to test him. He travels to Broly's location and challenges him. Broly, seeing Beerus as a threat to his friends or his planet, fights back with all his might.
One possible plotline could be that Cell, seeking to prove his superiority, challenges Broly. Broly, in his usual berserk state, accepts without hesitation. The fight could start with Cell trying out his various attacks like the Kamehameha - like Solar Flare and his physical strikes. But Broly's power is just too much and he starts to overpower Cell. However, Cell then reveals a new, hidden ability that he has been developing in secret and the tables are turned for a while.
A plotline could involve Broly being sent to Kale's universe by some sort of interdimensional rift. Kale initially sees him as a threat and attacks. But as the fight progresses, they start to understand each other's power and motives. Or perhaps a fanfic could have a story where both Broly and Kale are training on the same planet. Their training methods clash, leading to a fight where they both learn from each other and grow stronger in the process.
A plotline could start with Frieza hearing about Broly's power and being jealous. He then devises a plan to ambush Broly. But Broly, being extremely perceptive in his own way, senses Frieza's approach and is ready for the fight. As the fight progresses, Frieza realizes that Broly is much stronger than he expected and has to use all his dirty tricks to try and win. Or perhaps the plotline could involve Broly being captured by Frieza's forces, and then Broly breaks free and goes on a rampage against Frieza and his minions.
One idea could be that Broly somehow ends up in the world of Black Lagoon. He might initially be seen as a huge threat by the Lagoon Company. But as the story progresses, they realize his power can be useful against their common enemies. For example, when facing powerful crime syndicates or military forces that are too much for them to handle alone.
Well, they might be really shocked at the power levels of Goku and Broly. RWBY characters are used to their own kind of battles, and seeing the insane energy blasts and transformations in the Goku vs Broly fanfic could leave them in awe. They might start thinking about how they could incorporate some of those powerful moves into their own fighting styles.
In a Goku vs Broly crossover fanfiction, anime characters could have different reactions. Some might see Goku as a symbol of justice and be inspired by his never - give - up attitude. On the other hand, Broly's raw power could intimidate those who value brute strength. And there could also be characters who try to interfere in the fight for their own motives, like to stop the destruction that such a powerful battle could cause.
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.
I'm not entirely sure specifically what the 'black vs black 2 story' is. It could be a story about a conflict or competition between two black entities, like two black characters in a fictional work, two black - themed groups, or something similar.