He might isolate himself from the League at first. Batman is used to working alone, so he could retreat to his Batcave and plan his next move. He could also start to prepare counter - measures in case the situation escalates and the Justice League becomes a threat to him.
Batman might also try to communicate with individual members of the Justice League who he trusts the most. He would try to reason with them and show them that he has been wrongly accused. However, if they don't believe him, he would be even more determined to prove his innocence on his own terms, which could lead to some intense confrontations in the fanfiction.
Batman would probably isolate himself at first. He'd retreat to the Batcave to analyze the situation. He might feel a sense of guilt, thinking he should have seen the betrayal coming. After that, he'd start planning his counter - move. He'd use his vast resources and knowledge to expose the truth behind the betrayal and take down whoever is behind it.
Some members might be shocked and try to persuade him to stay. They know how valuable he is to the team, both in terms of his strategic mind and combat skills. Superman, for instance, might have a heart - to - heart talk with him, appealing to their long - standing friendship.
Some members might be shocked. Wonder Woman, for instance, who respects Batman's skills and tenacity, would likely be very disappointed. She might try to persuade him to stay, emphasizing the importance of his presence in the team. Superman, on the other hand, might initially be understanding, as he knows Batman has his own way of doing things. But he would also be concerned about the power vacuum that Batman's departure would create. Aquaman might be more indifferent, thinking that Batman was always an outsider to some extent, with his focus mainly on land - based issues.
The Justice League as a whole would have a diverse range of reactions. Some members like the Flash would be all for it, seeing it as a fun exploration of Batman. Others like Wonder Woman might use it as a way to understand how the public perceives Batman's role in the League. And then there are those like Aquaman who might just shrug it off unless it directly affects his interests. The fanfiction could also potentially create some internal discussions within the League about how they are all portrayed in the public's imagination.
The Justice League's reaction in fanfiction when Batman dies can vary greatly. Superman might become more withdrawn, feeling like he failed as a friend and protector. Wonder Woman could be the one to try and hold the team together, using her strength and wisdom. The Flash might struggle with guilt, thinking he could have been faster to save Batman. Each member would have their own internal conflict and way of dealing with the loss, which could lead to some interesting character development in the fanfiction.
The Flash might initially be in denial. He's used to Batman always having a plan and his death would be a huge shock. He would then turn his speed into a tool for investigation, trying to find out exactly what happened. Green Lantern could feel a sense of loss but also be spurred into action, using his ring to try and prevent future tragedies like Batman's death. He might create constructs in Batman's memory to inspire the team.
Some might be shocked. For instance, Batman is often portrayed in very different ways in fanfiction compared to his 'canon' self. Superman might raise an eyebrow at a fanfic where Batman is overly emotional. Others like the Flash might be really into it, finding the different takes on Batman's character and his adventures exciting.
Batman's sacrifice would likely have a huge impact on the Justice League. It could make them more determined to uphold justice in his memory. They might also become more cautious as they've lost a great strategist.
Batman could become more of an anti - hero. He might start working against the Justice League's interests, thinking that they have wronged him. He would use his skills and resources to expose any flaws in the League's operations and undermine their public image.
Batman might also play on the fears and secrets of the Justice League members. Since he is known for his detective skills and knowledge of people's pasts, he could expose or use those secrets in a way that makes the heroes feel vulnerable and scared. For example, if he knew of a deep - seated fear that Superman has, he could create a scenario that brings that fear to the surface. This would not only be a shock to Superman but also to the rest of the League who see their seemingly indestructible teammate shaken. Another way could be through psychological warfare. Batman is a master of the mind game. He could isolate members of the League, cut off their communication, and make them feel alone and in danger, which is quite a scary situation for heroes who are used to working together as a team.