My critique would be that this one´s superior to most of your artwork I´ve seen because it finally contains at least something in the description/artist´s comment section. Like all your artwork I´ve seen so far this is absolutely great design,especially in the field of those modern semi-SciFi concepts,you really have what it takes there and more,bringing me even to the thought that much of that "fashion" (which I like,not to take me wrong) could be even inspired by your work. But with that politics of mostly putting some nonsense below your artwork (at least here on dA),I think you create an impression of you yourself not taking your artwork very serious or not having th ecourage to do so,which then is mirrored by many viewers.
To me precise lines aren't everything in art. In fact, for the most part they're worthless; lines are inorganic.
That aside I would say that it feels at least somewhat unfinished -though 'concept' and 'quick' tended to make up for what few faults I can find. As another commenter pointed out: the legs are a bit out of place. I won't say "wonky" because they're angled and proportioned as one would expect, but the end of the barrel to 'his' weapon comes to an end where his legs part. For a moment I thought there was to be the idea that the weapon had just been fired, it looked liked smoke was pouring from the barrel. Upon closer inspection, though, it was apparent that the color of the backdrop and the incidental location of the end of the barrel caused the illusion. I don't know if that helps, calling back the key 'quick' and 'concept'.
try to make up two values in your head.. one is black and one is white. Now the values within each one of these two areas can never be put into the other one. So if its in light, its in light! and if its in shadow, its in shadow and try to be consistent with this because it will add to realism. When you've figured this out, you can use a degree of values in the light area, and a certain degree in the dark area ( depending on lighting situation and distance etc etc. )
The problem you have with the left under-arm is that it has a relationship with the values around the top-torso that is clearly in light.. while the lighting situation suggests that its in shadow, at least partially. you've also lost some saturation in the darker area of the underarm.. and saturation is another thing that is good to be consistent with.. Same goes for the legs.. and the plane the figure is standing on.. try to make more relationships for the shades.. and sorry for the long critique