In some fanfictions, a possible plot is that there's a dark influence on Batman. It could be something like a magic spell or a psychological break that makes him target Superman. Another idea is that the public perception of Superman turns negative, and Batman, being the protector of Gotham which is part of the world, feels he has to act. There could also be a plot where Batman and Superman are both being manipulated by a greater power, but Batman breaks free first and has to fight Superman to break his control as well.
One popular plot could be that Batman discovers Superman has been mind - controlled by some villain. So, in order to save Superman and the world, Batman has to fight him. Another plot might involve a misunderstanding. Maybe some false information leads Batman to believe Superman is a threat to Gotham, and he takes action. There could also be a plot where Batman is pushed to his limits by some external force that makes him see Superman as an obstacle, and he uses his wits and skills to take on the Man of Steel.
Lex Luthor is often an interesting character in such fanfictions. He might be the one pulling the strings behind the scenes, fueling Batman's distrust of Superman. Another could be Alfred. His wisdom and influence on Batman can add depth to the story. He might try to talk Batman out of fighting Superman or help him in a more covert way. And then there's Wonder Woman. She could be caught in the middle, trying to mediate between the two or having her own motives for getting involved in their conflict.
A common plot is that Malfoy spreads false rumors about Harry in the wizarding world. This causes problems for Harry, like making some students avoid him or look at him with suspicion. When Harry finds out that Malfoy is the source of these rumors, he gets angry and beats him up. There are also fanfictions where Malfoy tries to get Harry expelled from Hogwarts by framing him for something he didn't do. Harry, being the brave character he is, doesn't take this lying down and gives Malfoy a good thrashing.
Alfred is always a likely ally. His knowledge and experience can provide valuable support to Batman. Also, Oracle (Barbara Gordon) could be an important ally, using her hacking skills to disrupt any technology Superman might use or to gather information.
Alfred Pennyworth is quite popular too. He can offer his wisdom and support to Batman, and his interactions with Superman can be both humorous and heartwarming. He's like the glue that holds things together in the Batcave, and his presence can bring a sense of home to the story.
Lois Lane is often a popular character. In fanfiction, she might play a crucial role in mediating between Batman and Superman or getting involved in their adventures in a more hands - on way, using her investigative journalism skills.
One popular theme is the exploration of their complex relationship. Fans often write about how Batman and Superman, with their different ideologies, come to understand and respect each other on a deeper level. Another common theme is the two heroes teaming up against a greater threat that neither could face alone. It could be a super - villain who has found a way to neutralize their individual powers. And sometimes, the theme of friendship turning into a more intense emotional bond is also explored in these fanfictions.
One popular plot is the discovery of a common enemy that forces Superman and Homelander to team up, despite their differences. Another is a battle for supremacy in a world where both exist, with different factions taking sides. And then there's the plot where Superman tries to reform Homelander, seeing the potential for good in him.
Catwoman can also be a popular character. Her ambiguous moral standing and her relationship with Batman can create interesting sub - plots in the fanfiction. She might get involved in a scheme that involves both Superman and Batman, either as an ally or an adversary depending on the story.
One popular theme is the love triangle between Superman, Wonder Woman and Batman. Writers often explore the complex relationships that could develop among them. Another theme is them teaming up against a powerful enemy that none of them could defeat alone. This shows their combined strength and the importance of their alliance in the DC universe.
One of the popular ones is 'The Dark Knight Returns' which features an older, grittier Batman. It's a classic that redefined the character in many ways. Another is 'Superman: Red Son' which presents a very different take on Superman's origin and his relationship with the world. And 'Batman/Superman: World's Finest' which has great stories about their team - ups and the dynamic between the two heroes.