Lex Luthor would be a great antagonist. He could play on the differences between Batman and Superman, trying to turn them against each other while he pursues his own evil plans. Maybe he creates a situation where it seems like Superman is a threat to Gotham, causing Batman to be on high alert.
Lex Luthor would be a great choice. He's Superman's long - time nemesis. He could form an alliance with some of Batman's foes like the Joker. Luthor could use his intelligence and resources to create a plan that only Superman and Batman together could stop.
One idea could be that Batman and Superman have to team up to stop a new villain who has the power to manipulate time. This would put their different approaches to justice to the test as they race against the clock.
One idea could be that Superman and Batman have to team up to stop a new supervillain who has the power to manipulate time. This would force them to put aside their differences and work together in a really challenging situation.
Lex Luthor would be a great villain. He could be plotting to destroy Superman once and for all while also trying to outsmart Batman. His intelligence and resources make him a formidable foe for both heroes.
One possible reason could be mind control. Maybe some villain has taken over Superman's mind and made him do it. Another reason might be a fundamental difference in their ideologies that has escalated to the point of no return.
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.
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.
A cool plot could be that a powerful alien race arrives on Earth and offers a deal to the world leaders. Batman is suspicious of their motives and starts investigating. Superman, on the other hand, is more open - minded at first. This causes a rift between them. As Batman uncovers more evidence of the aliens' true intentions, he has to convince Superman. In the end, they join forces to stop the aliens from taking over the Earth.
In Batman and Superman fanfiction, 'stranger danger' can be depicted in various ways. For example, a new villain could be introduced who is a stranger to the city and poses a great danger. The heroes would then have to figure out the stranger's motives and powers to stop them. It adds an element of mystery and suspense to the story.