So... dude, this one is sick, I love so much how it looks, I feel like I can never seem to try and paint something as ambitious and cool as this piece, congrats it looks amazing, I even feel like I am not good enough to give a helpful critique here, but let's try it. In my opinion, theres nothing wrong on painting fanart specially If you feel like doing so, yes, the design is right there already, but that's not cheating, when a fine artists works with a model is he cheating? I don't think so, but, if your goal is eventually to make your own designs and work from imagination, you might want to do that too often, so switch it up from time to time, working from reference is a must, so you are doing excellent, just try doing both. Now onto the critique itself. There was little to change since the image already was working really well. The main few things I noticed was that you should be using warmer colors in your lights given the background the character is in. Also try and make stronger shapes, group them and turn up the contrast just a bit to make the image more dramatic. For the "stiffness and emotionless" that you mention, I think the stiffness works for this, and the darker shadows on the face I added make me feel like he really is going to end the X-men for real this time, he looks more menacing now. I suggest using some background music to put yourself on the mood for the painting you are doing, this always helps with the emotion side of a painting, (I was listening to Ludwigs Göransson's Odyssey Soundtrack since I watched the movie just yesterday haha). I also used the background to pop up the silhouette and help the overall read of the image, pushed the proportions just a bit, darken the fist at the bottom right since we don't care about it here. That's pretty much everything (I'm sure I forgot to mention some other smaller change I made) I hope it helped and again, it looks awesome, keep going. I also love the X-men btw | Artwod Feedback