What could be the plot of a 'Ben 10 Justice League crossover fanfiction'?

One possible plot could be that the Omnitrix malfunctions and sends Ben 10 to the Justice League's universe. The Justice League initially views Ben as a threat due to his alien forms. But as they learn more about him and the threat of an inter - dimensional villain, they team up. Ben's different alien forms offer unique skills that complement the League's powers, and together they fight the villain to save both universes.

Well, the plot might involve a powerful alien entity that has the ability to disrupt the fabric of reality. This entity targets both Ben's world and the world of the Justice League. Ben, being the hero he is, gets caught in the middle and has to seek help from the Justice League. They don't trust him at first, but when they see him in action, like when he turns into XLR8 to quickly gather information about the entity. Eventually, they join forces. Ben's alien form Cannonbolt can be used to ram into the entity when it's in a vulnerable state, and the Justice League uses their combined powers to weaken it further until they can defeat it.

In a 'Ben 10 Justice League crossover fanfiction', perhaps the Forever Knights somehow manage to cross over to the Justice League's world. Ben, following them, ends up there. The League is intrigued by Ben's Omnitrix. They start working together when they find out that the Forever Knights are teaming up with Lex Luthor to steal technology from both universes. Ben uses his aliens like Heatblast to deal with Luthor's heat - based weapons and Four Arms to handle the Forever Knights' brute force attacks.