Oh wow. I love the darkness of this! Great shading and use of contrast, too. And all the details on Loki's armour ofcourse, those are amazing! You make it look like it's easy to draw while I think it's actually really hard.
Hehe, the hardest part is to keep going! You know when you start a drawing and suddenly you think 'I can't draw, why am I even trying this!?' And to keep going then, that's the hardest part. Well, besides getting the face right, if you're drawing someone who has to look like themselves, haha!