Good
I'm not really much of a stick fight fan. But as far as mechanics go, the black stickman punching the other black stickman at the very end looked more realistic. Well, the punch did, the result (the guy flying into pieces) didn't.
For the red vs blue fight, if the red guy leaned in more with each punch, it'd look like he's throwing more force in the punch. As it was, the sound effect was making his punch seem heavier than it was.
If you want to get technical, a punch is more than just throwing your arms out at someone. A strong, solid punch requires flexing muscles from your fist, down your back, down the leg and into the foot, which needs to be firmly planted--I guess you can say a good punch begins at the foot. I believe most of the power of a punch comes from the back, so your stickman's back would tilt and curve forward at least. The greater the angle from foot to fist (to a point), the greater the power.
Without the back curving, the punches look more like slow jabs to me. If they are jabs, speed them up.
During the kick, it looks like the red guy is a bit too balanced (too vertical). Adding more tilt would add to the illusion of power--and possibly add personality to the animation. With any movement, the more balanced you make the guy, the less effort he seems to be exerting.
It looks like the red guy is hitting a force field because the blue guy doesn't react at all to being hit--but, maybe he's a Hulk or actually has force fields. Don't know if it was intentional, but since he remains balanced, it looks like he exerts no effort in blocking. Not necessarily a bad thing.
But since he remains balanced during his punch, it looks like he's pulling his punch. But if he's superhumanly strong, a little effort would make a great impact.
But still, good animation.