Superhero stories can be fun but also incredibly difficult to write—think Marvel or DC movies but in book format. You need to be able to balance a lot of things: character development, plot, realistic technology/powers, and a believable conflict. Here are the basic elements you need in order to craft a superhero story.
A hero
The hero is what drives your story forward. They need to have some internal insecurity, and their power/technology that allows them to be superhuman doesn’t help.
First, give your hero a believable power—and remember to give it limits! Superhero stories are a form of fantasy, but all fiction has to be realistic in some sense. The reader won’t trust you if your hero can do anything without any consequences. Let the power complement their greatest strengths but also highlight their faults.
And don’t forget that your superhero is also a person. They need to have a plausible story line with plenty of growth. They should have a personality, friends, family, faults, strengths, a job.
A villain
This can be a supervillain with powers or an otherwise powerful person without technology/magic. Again, they need to be a person too. It’s not believable if your villain is all evil. They should have a good and a bad side, with likable traits and unlikable traits.
Make sure they highlight the different between themselves and the hero. Give the reader a reason to root for the hero, even if it’s just because they’re a little bit worse than the hero.
A conflict
Like any good story, a superhero story needs to have a conflict. Your hero has to be fighting for something, and your villain has to be standing in the way of that.
It needs to be realistic, too; you can’t just throw two characters together and expect them to hate each other. There can be a backstory between them, or a bad first impression, or maybe the villain is known for being a terrible person and the hero is incredibly pious.
A solution
Most superhero stories end with the hero winning. You can go in this direction or the opposite way, where the villain succeeds.
Your ending still has to be clear and make sense. The reasons why the story ended the way it did need to be made obvious throughout the story: did the hero or villain slip up somewhere they shouldn’t have?
You can give a final image of the world after (the hero’s life or the villain’s life) or leave it up to the reader’s imagination.