It could be about various things. Maybe it's a fan - written story that focuses on the death of Batman within the fictional universe created by fans. It might explore how other characters react to his death, like Robin taking on more responsibility or Gotham falling into chaos without its Dark Knight.
It could be about the end or cessation of fan - created stories related to Batman. Maybe the fanfiction community for Batman has declined, leading to what is seen as 'the death' in terms of new works being produced, or perhaps it refers to a specific storyline within Batman fanfiction where the character of Batman actually dies.
Definitely Batman, whose death is the focus. Then there's Nightwing, who has a long history with Batman and would have a big part to play in the story after Batman's passing. Alfred, as Batman's loyal butler and friend, would be prominent. And don't forget Catwoman. She has a complex relationship with Batman, and in a story about his death, she could be a main character, either mourning his loss or trying to take advantage of the power vacuum in Gotham.
One reason could be the oversaturation of Batman content in official media. With so many movies, TV shows, and comics already out there, fans might feel less inclined to create their own stories.
Superman can also be an opponent in some 'death battle batman fanfiction'. It's an interesting match - up as it pits Batman's brains and preparation against Superman's superhuman strength. Writers often explore how Batman could potentially defeat someone so much more powerful.
Perhaps a member of the Justice League, accidentally. For instance, during a fight where powers go out of control. Let's say Flash runs too fast and accidentally knocks Batman into a sharp object, causing a fatal injury. This would create a huge moral dilemma within the League.
She could be devastated. Wonder Woman might go into a period of mourning, isolating herself from others as she grapples with the loss. She was used to having Batman as an ally, and his death would leave a big hole in her life.
One interesting 'death battle batman fanfiction' could be where Batman faces off against an otherworldly demon. In this story, Batman uses his wits and a new set of high - tech gadgets he's developed. He has to outsmart the demon's magical abilities with his strategic thinking.
Grief is a very common theme. All the characters who were close to Damian, like Batman, Robin (if there's a new one), and the rest of the Bat - family, have to deal with the intense pain of losing him. Another theme is revenge. Batman might be driven to seek revenge against those he believes are responsible for Damian's death.
The death of Batman in fanfiction can cause chaos within Young Justice. His death means the loss of a great strategist. Without his plans and guidance, the team may find themselves in over - their - heads during battles. They'll need to quickly learn to rely on their own instincts and develop new strategies.
One interesting crossover could be Batman getting his hands on the Death Note. He would likely be very conflicted about using it. On one hand, he could potentially rid Gotham of its worst criminals without having to physically fight them all. But his strong moral code would probably prevent him from using it, as it goes against his belief in justice through the legal system. Another aspect could be L from Death Note trying to figure out Batman's identity, using his detective skills which are somewhat similar to Batman's own.