Have you built up enough suspense and action in the previous pages of the story to prepare the reader for a big fight scene? Your protagonist and your antagonist may play cat and mouse throughout the novel, leading to a showdown fight at the end of the novel. Or your protagonist may be trying to save a key character by fighting the antagonist. There may be multiple characters involved in the fight or just two characters. Think about what purpose the fight scene will serve in your story and how it will advance the plot.
Note how many characters are going to be in the fight scene, and where the fight scene is going to take place. Consider the time of day, the mindsets of the characters involved in the fight, and the stakes of the fight. Will it be a fight to the death or a fight with minor injuries?