OK, I like the design, but one observation I would make is the “additional elements” seem very thrown together. By additional elements, I mean the costumes stuff that isn’t the spandex part, so the helmet, shoulder pads and robotic arms. The helmet and robotic arms work together, but are coloured differently, meaning the shoulder pads look slightly out of place with them, but they carry over with the spikes elsewhere on the costume (and again, they’re a different colour to the other two). My advise would be, darken the brown on the pads to match the costume and change the gold on the robot arms to match. Match the greys on all three plus the arms spikes (the helmet is a bit off here atm) and maybe add something like a tech insignia or another more techy shoulder pad underneath the current shoulder pads, so as to integrate them with the design a bit more.
Other than that, the pose is great, has a real sense of action which I like. I like the brown, grey and green colour-scheme (which is why I think you should change certain colours on certain items) and the minimal use of the vivid green means it really catches your eye and draws you to those parts. So, overall, great job, just a few tweaks and then it’s perfect.
Oh, just noticed another minor thing to tweak, maybe move the back right arm down a bit or making a tiny bit larger, because the position it is in at the moment means his shoulder isn’t attached to his body in any way.