First things first your anatomy is WAY off, but it's clear enough that I can tell what you were going for. I'd suggest you Google "Human Body Maps" (I'd post a link but I'm not sure if that's allowed) just so you get a better idea of how muscles fit together and what goes where. Secondly (in my opinion) the lines on the exposed parts of their body seem too thick in some areas (like the torso). It's a bit jarring to look at when compared to the much cleaner and thinner lines on the robot arm and armor. BUT the image is really clean, the colors are good, the character design is really cool, and the textures really make the the metal look like metal (also the use of white highlights isn't too shabby either). So overall I'd say that skill you show with colors, textures, and character design almost completely make up for the funky anatomy.