One possible storyline could be that Batman discovers a conspiracy within the Justice League that endangers Gotham. So he and Robin decide to take on the League to stop it. Another could be that the Justice League is being mind - controlled, and Batman and Robin are the only ones who realize it and try to free their friends by fighting them. Or perhaps there's a misunderstanding where the Justice League believes Batman and Robin have turned bad, and they have to fight to prove their innocence.
A storyline could involve a new villain who has the ability to manipulate the Justice League against Batman and Robin. Batman and Robin then have to find a way to break the villain's hold on the League while also fending off their attacks. Another idea is that Batman creates a new technology that the Justice League wants to take from him for what they believe are the right reasons, but Batman and Robin see it as a threat to their autonomy in Gotham. This leads to a conflict between them. There could also be a story where Robin is kidnapped by a rogue member of the Justice League, and Batman has to take on the whole League to get him back.
Another storyline might involve Batman leaving because of a personal crisis. For example, he discovers something dark about his past that makes him question his place in the Justice League. He might think that he's a liability to the team and decide to leave to protect them.
One possible storyline could be that Goku Black arrives on Earth in search of a powerful energy source. The Justice League detects his arrival and confronts him. At first, they underestimate his power. Goku Black easily defeats some of the members, but then the League starts to work together and figure out his weaknesses. Another storyline could be that an evil entity has brought Goku Black to the DC Universe to cause chaos and the Justice League has to stop him while also dealing with the entity. Or perhaps Goku Black is tricked into thinking the Justice League are enemies of the Saiyans and he attacks them, only to later find out the truth and have to team up with them to fight a greater threat.
Well, in a battle between Batman and Robin vs the Justice League, it's really tough to say. Batman is known for his incredible strategic mind and vast array of gadgets. Robin, depending on which one, also has some skills. But the Justice League has some of the most powerful beings in the DC universe like Superman with his super strength, speed and heat vision, Wonder Woman with her combat skills and Amazonian powers. However, Batman has been known to take on foes much more powerful than him with his wits. So it could be a very close fight if Batman and Robin could use the right tactics.
One popular storyline could be an alternate universe where Batman has to lead the Justice League against a powerful, mind - controlling villain that has turned most of the world's population against them. In this, Batman uses his detective skills to find the source of the mind control while also trying to keep the remaining members of the Justice League from being captured.
One possible storyline could be that Batman sacrifices himself to save the world from a powerful alien threat. He uses his intellect to devise a plan that requires him to give his life. Another could be that he is poisoned by a new villain in the Justice League Unlimited universe, and despite the efforts of his friends, he succumbs to the poison.
Perhaps there's a story where Batman joins the Justice League just in time to help prevent an alien invasion. The League is struggling against a technologically advanced alien race, and Batman's strategic mind is the key to formulating a plan. He uses his resources and knowledge of Earth - based technology to create counter - measures against the alien weapons. Along the way, he forms bonds with his new teammates, especially with Wonder Woman, who respects his tenacity and intelligence. This experience makes him more integrated into the Justice League and changes his perspective on the larger scope of protecting the world.
One main conflict could be their different approaches to justice. Robin might be more impulsive and want to take quicker action, while Batman is more methodical. Another could be Robin trying to prove himself as an equal rather than just a sidekick, which could lead to clashes. Maybe there are also differences in how they view the use of certain tactics or their relationships with other characters in the Young Justice universe.
One popular storyline could be a time - travel adventure. Imagine Batman Beyond getting accidentally sent back in time to the era of the original Justice League. He has to team up with the younger versions of the heroes to stop a threat that could change the future. For example, a villain from his time could have followed him back and is now trying to rewrite history to gain ultimate power.
One interesting storyline could be the Justice League having to deal with a mind - controlled Batman. Maybe some villain manages to take over Batman's mind, and the League has to figure out how to stop him without harming their friend. It would be full of action as they try to outwit Batman's strategic plans while also trying to break the mind control.
A possible plot idea is that Batman discovers a dark secret within the Justice League that they are unaware of. This secret could be something that could potentially destroy the League or change their moral compass. Batman then has to decide whether to confront the League directly or try to fix the problem on his own, which causes the 'vs' situation as the League may see his actions as a threat.