The main antagonist would be the Flashpoint Joker. In the Flashpoint universe, he is likely to be even more dangerous and unhinged. He could be targeting Batman directly or causing destruction that Batman feels responsible for stopping. His presence would drive the plot forward as Batman tries to outwit and stop him.
Well, it could be about Batman trying to stop the Flashpoint Joker from causing chaos in Gotham. Maybe the Joker has a new and devious plan that only Batman can foil.
Well, obviously the two main characters are Batman from the normal DC universe and Flashpoint Batman. Batman is the well - known Dark Knight, a symbol of justice in Gotham. Flashpoint Batman is from an alternate timeline, with different experiences and a potentially different personality.
Another plot development could be that Flashpoint Batman tries to convince the regular Batman to change his ways. He might see the regular Batman's methods as too soft or ineffective. This could create a lot of internal conflict for the regular Batman as he questions his own beliefs and methods in the face of this alternate - self's criticism.
The main similarities are the high stakes and the presence of these iconic characters. However, differences can be seen in the way the story unfolds and the challenges they face. For instance, the Flashpoint version might have alternate backstories or motivations.
The Riddler could be a great main antagonist. He loves to create complex puzzles and mysteries, which would be right up Sherlock Holmes' alley. And of course, Batman has had his run - ins with the Riddler in Gotham. Holmes' deductive skills and Batman's combat and detective skills would be put to the test trying to outwit the Riddler's convoluted plans.
It could be Darkseid. He's a powerful and well - known villain in the DC universe. His goal of universal domination would put him in direct conflict with the Justice League and Batman's determination to protect Gotham and the world.
In this comic, the story is set in a changed reality. Batman and Joker's conflict reaches new heights and has unexpected developments. It's full of action and drama.
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.
Ra's al Ghul could also serve as the main antagonist. He might have a new plan for Gotham that involves using Catwoman as a pawn. He could be aware of her relationship with Batman and try to use it to his advantage. Batman would have to not only save Gotham but also rescue Catwoman from Ra's al Ghul's clutches.
The Joker and Batman are the key players. However, in some fanfiction, other characters from the Batman universe might also play important roles, like Harley Quinn who has a close relationship with the Joker, or Commissioner Gordon who is often involved in the Batman - Joker dynamic.