You forgot to mention that I helped you with the shading/outline on pigmite and razoboar ;D
But anyways nice sprites the only one I would worry about is proton.
Now lets look at the outline on this. First of all its pretty rough, which we don't want we want some smooth lineart so it looks more appealing and not so scratchy. I found a tutorial on lineart that should help you on it.
link
I would also take away the lines that hold the little atom balls. It seems to get in the way of the sprite and in my opinion it would look much better without it.
Lets get on with the shading, You have literally the shading and the lighting literally all over the place. On the upper portion of the body it should have more lighting less shading and on the lower portion more shading and little to no lighting. Remember the sun is always facing in the top left hand corner and if any body parts get in the way of it, there should be shading in the shadow of the body part.
Now I like the overall design I just feel its missing arms :/
Otherwise its fairly nice.
Anyways some things you might want to work on Haroun otherwise its a fairly decent sprite <: