Looks good and promising. Although Helm's comment on the back of the head is valid, you can take creative liberties from literal realism because it's a cyborg, which can exist with not as many parts as a human. The features on the face do seem to wobble quite a lot, the left eye too big, high and out of perspective regarding the one on the right, the forehead lacking further highlighting and volume, and the forehead transition from face to mechanical parts also incorrect on perspective. To check for these errors, why not go for the tried and true method of "Mirror all Layers"
I suggest you keep in mind, rather than meticulously rendering every detail and getting a somewhat busy result in places, render with the aim of hinting at texture, sacrificing some detail. I'm thinking mainly the head tubes (which also need increasing volume by more highlighting and darkening), and the ribs (while looking good, are maybe too detailed).
Also, something about the palette just doesn't feel right to me. Probably the desunification between the flesh tones and the metallic ones. I think the flesh midtones need less saturation, maybe a lot less.