I quite like it, it's sharp and punchy, though I recommend that you add at least one frame of anticipation at the start to make it less sudden and give more weight to the punch.
Also I enjoy the personality of the foe as he gets hit, but the main character could use some stronger expressions as he's punching the guy himself. Like maybe an eye widening as he finishes the first, second punch has his eye stretch perhaps and his third is really wide and the mouth is more stretched out (to make it more a roar look rather than just him opening his mouth) (Exaggeration is certainly an option you could take here and it would look quite nice)
Also perhaps the enemy having light hitstun flashes or some sort of effect would help increase the feel of impact on him, it's a nice old school brawler convention.
Also his punch upwards as some rather rough smears, it sorta looks like afterimages but in motion it look a bit odd. I reckon just smooth it over into a solid stroke instead of multiple strokes so that the top's jaggy nature doesn't affect the flow.
Idle's solid though, got nice bounce. And the punch animation is nice and clean with a very natural flow. So nice job, I'm glad to see more of this game.