I noticed you updated your post PivotYoungster, but you only edited it. If you want people to see that it's been updated, you have to also make a new post saying "Update" or whatever you want to say. Doing this will bump your thread to the top.
Running loop has good flow and the arm re-sizing looks nice.
Little jump needs more easing. When the stick-figure anticipates the jump by bending down, he stops very suddenly which doesn't look good. When he lands, again it comes to a sudden stop which makes it look stiff and unbelievable. If you apply easing in these areas so that it doesn't stop abruptly, it will look better. Easing is the slowing down and speeding up of movement over a series of frames.
Punching looks good but it's short so it's hard to give much advice on. It all looks good to me though.
Little combo has shaky movements, most obvious in the part where he does his final kick, puts his foot back down and stands up. Shakiness happens when you don't space consistently over the frames. Spacing is the amount of movement from the previous frame to the current frame.
("|" = frame, "-" = spacing amount)
Shaky:
|-|---------|--|------------|-|------------|---|-----------------------|-------|-|
Smooth:
|-|---|--------|--------------|------------------|-----------------|--------|---|-|
Can you see how the spacing in the shaky example is very small one frame, very large the next, then very small again? Whereas with the smooth example, the spacing doesn't change erratically frame to frame. Instead it is consistently the same speed, or if it changes speed it happens gradually over multiple frames.
So I think if you just pay attention to your spacing and your easing you'll improve a lot. Right now I think you have potential, and some of the animations actually look good, like the run loop and punching animation.
There is
Mitch's tutorial which might help a lot as well.
. I need to work on my reactions too, I don't know how to do it. I can only animate an attacking stickman.
