Lighting is off, especially in the highlights: the head suggests a weird frontal light, while the shoulders have a strange upper light...
A good rule of thumb is that two shades shouldn't touch if you already have one that can go in the middle (excepting when you want to show a big light contrast in a low-res piece)
Also, your brightness shade a jump in brightness that's too big, in my opinion
The head has a protuberance approximately where the eyebrows should be which (the blue eyes help) reminds me of Dragon Ball characters
I think that in general, you placed the colors attending to the outline of the shape, instead of the lightning source.
The torso was also bugging me, I think you left a space too big between the armpits and the shoulders
Quick edit in which I mainly went for the head:

(I think I should have put the forehead highlight more to the left, but anyway)