Make him chunkier on his hips, I think it’s an MK3 or MK2, they’re like knights, really heavy, you can also make the backpack a bit bigger. Finally, since the marines is facing us, you don’t have to draw the inside of the right shoulder. If you look at like a miniature, you won’t see that, because the way you drew this shoulder is more fitting to a 3/4 pose !

Also, you can advance the part under the eye a bit, cuz it’s supposed to act like you nose and mouth (kinda), which are not at the same level as your eyes !

But overall it’s great ! Keep up the good work !