I kinda like your style, it needs improvement, but the hits really seemed powerful because you (somewhat) animated the full punches, the sounds, shaking, and that video-game-fighter-like “pause” on big hits while the screen shakes

its smooth too

now, to improve, you should focus on keeping the bodies acting and looking like real life

meaning, feet placement, that’s for one – they’re all over the place, they don’t seem to be standing or running but rather floating

imagine yourself actining out an action before you animate it, notice how your foot is placed, how your weight shifts, how you build up / anticipation for a punch (arm back, lean back, pause…then swing forward at high speed) – all of this should appear in your frames

don’t just simply move pose-to-pose, rather, animated how the people move from pose-to-pose

example, jumping, what you’re missing mainly is that “anticipation” phase