The Joker could still be a major villain. Even with Batman as a god, the Joker might find some twisted way to challenge him. Maybe he'd try to drive Batman to use his god - like powers in a way that goes against his moral code. Ra's al Ghul could also be a villain. He might see Batman's new godhood as a perversion of the natural order and seek to destroy him.
One possible plotline could be Batman using his new god - like powers to completely reform Gotham in an instant. He could eliminate all crime, poverty, and corruption with a single thought. Another might be him facing off against other god - like beings from different mythologies who see him as a threat to the balance of power in the universe.
The Joker could be an antagonist even when Batman becomes a god. He might see Batman's new status as a challenge and try to bring him down to his level through his usual chaotic and insane methods. Maybe he'd try to drive Batman mad with the idea that his new powers make him no better than the villains he fights.
Perhaps in the 'batman becomes a god fanfic', a plotline could involve Batman facing off against other god - like entities. He has to prove himself worthy of his new status among these powerful beings. This could lead to epic battles and alliances as he tries to protect not just Gotham, but the entire world or even the universe from threats that only a god - Batman could handle.
One possibility could be that Batman, after facing one too many betrayals in Gotham, decides to take a different path. Maybe the constant struggle against crime with little real change in the city makes him cynical. He could start using his skills and resources to control the underworld instead of fighting it. For example, he might start dictating which criminals can operate and where, creating a new order that is still dark but under his command.
If Batman becomes Joker in fanfiction, Gotham would be in chaos. Batman is the symbol of justice and order, while Joker represents chaos and anarchy. Without Batman to protect the city, criminals would run wild. And as the new 'Joker', Batman might use his intelligence and skills in a very different and dangerous way, perhaps creating more harm than good.
If Batman becomes a Lantern in fanfiction, he would gain the power of the Lantern ring. This could enhance his combat abilities even further. He might use the ring's energy constructs in his crime - fighting, creating things like shields or grappling hooks. His detective skills combined with the Lantern powers would make him an even more formidable force in Gotham.
There's a fanfiction that focuses on Bruce's training with different martial arts masters around the world as part of his transformation into Batman. It shows his struggles, both physical and mental, as he tries to master the skills needed to fight crime in Gotham. The story also delves into how he acquires his high - tech gadgets during this time.
In a fanfiction where Batman becomes immortal, one possibility is that he would become extremely jaded over time. He has seen so much death and destruction in Gotham, and with immortality, that would only continue indefinitely. He might start to question his own motives and methods. Also, his relationships with other characters like Alfred, Robin, and Commissioner Gordon would be strained. They would age and die while he remained, which could lead to him isolating himself from the mortal world.
In this fanfiction, Izuku could be inspired by Batman's lack of superpowers but still being a formidable hero. He may start training in more martial arts and stealth techniques, similar to Batman. And he could even create his own set of gadgets, like grappling hooks and smoke bombs, to aid him in combat and rescue missions.