To start writing an Arkham Knight fanfic, think about the theme you want to convey. It could be about redemption, like the Arkham Knight finding a new path, or it could be about the power struggle in Gotham. Next, create an outline. Outline the main plot points, the rising action, the climax, and the resolution. This will help you organize your thoughts. Also, don't be afraid to add your own unique twists to the characters or the story. For example, you could give the Arkham Knight a different motivation than what was shown in the game.
Begin by choosing a specific aspect of the Arkham Knight universe that interests you. It could be the technology in Arkham Knight, like the Batmobile or the villains' gadgets. Then, build your story around that. When it comes to writing, start with a strong opening that grabs the reader's attention. You can introduce a mystery or a conflict right from the start. As you write, keep in mind the tone of the Arkham Knight series, which is often dark and gritty. Use descriptive language to bring the world of Gotham to life in your fanfic.
First, you should have a clear idea of the story you want to tell. Decide if it's going to be a prequel, sequel, or something that takes place during the events of the Arkham Knight game. Then, do some research on the characters. Know their personalities, backstories, and how they interact in the official lore.