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.
Definitely not. Justice League is a creation of DC Comics. Marvel Comics has its own set of superhero teams and characters that are distinct from those in the Justice League.
They might be really surprised. Some fanfictions could show their characters in very different ways than they expect. For example, they might see relationships between characters that they never thought of in the official story. It could be both amusing and a bit strange for them.
Batman is often a very popular character. In fanfiction, he can be portrayed in different ways, like a more nurturing mentor figure to the Young Justice team or as a master strategist leading the Justice League in complex battles.
Some of them might be amused. They could find the different takes on their characters and stories quite entertaining. For example, Superman might chuckle at a fanfic that has him in a comical situation.
A third interesting storyline might involve a secret alliance between a member of the Justice League and a villain that the Young Justice team discovers. This discovery then sets off a chain of events where the Young Justice team has to decide whether to trust the rest of the Justice League and how to handle this new information without causing a complete breakdown in the superhero community.
One of the top stories could be 'Tower of Babel' which shows the vulnerabilities within the Justice League when their secrets are used against them. Another might be 'The Darkseid War' that involves an epic battle against Darkseid. And 'Crisis on Infinite Earths' also has a significant impact on the Justice League's story as it reshapes the multiverse they exist in.
The Justice League typically includes well-known heroes like Superman, Batman, Wonder Woman, The Flash, Green Lantern, Aquaman, and others. These characters form the core team.
The 2017 Justice League movie isn't from Marvel Comics. It's part of the DC Comics franchise. DC has its own unique set of heroes and storylines that are distinct from those of Marvel Comics.
It's hard to give an exact number because new comics are constantly being released. But there are definitely hundreds of Justice League comic issues over the years.