oversaturation. blanket shading along with blanket dithering here and there. Worst thing is the plastic over the left arm by far in that respect. However you've got some good volumes, in the plastic around the face mostly. The hair is way too red, generally your colour ramps are uninteresting in that they are primary colours with little hue intermixing or variation. unify the palette I say.
Avoid scribbly detail on the gun. It's a piece of metal and used by an x-com marine. I'd keep mine clean to get those damn Crystalids. Using harsh gray highlights on the gun somewhat indiscriminately.
True to the original game theme, but not in style. I'm cool with that. When it is more finished, by critique will be more definite.