In my opinion, these are essential for fight scenes:
Motivation. I want to know why your characters (on both sides) are fighting and why. What are the stakes? What will happen if they lose / win? Is there a danger of serioussevere injury or death to make me care about the outcome?
Tactics. Reading "he hit him, and then he hit him back, etc." isn't engaging for most readers. What are the more understandable ways that characters are using to try and win the fight? Do they work? Are they countered? What will the character do next and how does it affect them?
Emotion. How are the characters who I care about dealing with the fight? Are they afraid? Confident? Angry? Desperate? Emotions run high in battle, and though it's tricky, it's good to play on them and bring them out.
Position. In big, complicated fights, where is everyone? Fights need to be written simply, quickly, intensely, but I still need to know who is fighting who and how far away from each other they are because it can get confusing or difficult to visualise easily. (And that's not to mention when characters I thought were in one place turn out to suddenly be in another...)