Oh, this drawing is yours as well.. I just searched for Warhammer 40k and found a few good drawings.
Anyway, I'll pretty much repeat what I just said about the other Astartes. Helmet looks perfect on this one though, but the shouler pauldrons need to be a bit bigger and bulkier. Also, the thunder hammer on this one looks tiny. (And I've never seen or read a single lightning claw being used in unison with a thunder hammer - this though, isn't impossible imo. It's just usually a power fist and a hammer..)
Small shoulder plates. A thunderhammer is a bit too small as well. The wires from hammer should be going under the shoulder plate, not wrist. And the face. Breather, to be specific. I think it needs correction. Beside of all that, pretty good work. Continue and improve your skills.