From my experience watching a lot of action films, the moments that feel the most realistic are usually the ones where the choreography looks messy and the characters clearly struggle. A few months ago I spent some time reading about famous fight scenes and how they were filmed, and I found an article at https://theactionelite.com/the-most-brutal-hand-to-hand-fight-scenes-in-cinema-what-makes-them-perfect/ that explained many of these details. I used that page mostly to understand how directors combine camera movement, sound design, and actor performance to make every hit feel heavy. After that I started noticing small things during movies, like pauses between strikes or the way characters lose balance for a moment. Those details create tension and make the audience feel the physical effort instead of watching a perfectly clean fight.