looking nice, but I think those mechanical parts are a bit too smooth. a degree of smoothness is necessary for realism, but I think it's just a bit too round. Regardless, nice details. Beef up that arm with some cables and you should be good
(by the way, I think your robot's jaw may look cooler with a few layers of teeth. Shark's teeth, if that's the look you're going for, are aligned in this way-layers- and I think it might give the jaw a nice touch)