Sonic Boom's Sprites!

[Silverthorn]

I'd try to focus more on the faces of the character a little. Yours have comparably large eyes, no eye brows, and very small pupils.

Ie. compare and

Also, your shading is fairly strange. Try to keep it simple rather than using repetitive shapes (unconsciously, I had to think of fish bones :p). For reference, just check out some sprites where hard shading is applied (I know, mine are exactly the anti-example with tons of gradients etc xD); the shadows are where they need to be, no additional going-crazy with clothing-folds etc.

So yeah, and, with the uppercut, try to blend the fist and the trail a bit better by removing those darker pixels and unifying the colors (aka. make the trail more cyan or the fist-glow more blue).

Keep it up!