Hello! First off I'd like to say that my review is in no way impacted by my love for Tom Hiddleston.. >.>
The color palette that you chose for this piece is delightful; the greens and blues from Loki's coat and staff really steal the show. And honestly, my only complaint about the color is that there's so much...yellow. A wonderfully painted yellow, mind you, but it gets a bit overwhelming to the point where I think of the short story "The Yellow Wallpaper" when I look at it. (Though Loki is a bit of a nutter himself, is he not? Ehehe. Anyway.)
You've managed to articulate his garments very well. Watercolor can get "mushy" but your lines are crisp in all the right places; it is easy to see where layers overlap (bottom of jacket and leg, forearm and chest) while still looking cohesive. The touches of pattern here and there are a nice touch as well, though the pattern on the green at the bottom of his coat gets a bit "loud" compared to the rest of the composition. Still, it creates a new level of interest and makes the detailing on the cuffs and pauldron less isolated. So it's a double-edged sword, I suppose.
The way you've handled the background and staff are particular favorites of mine. Already talked about the background color a bit, but I feel it prudent to mention that I truly enjoy the technique you've used on it to create some additional texture, and which is again mirrored in Loki's coat.
Overall, I give this piece 4.5 stars out of 5. The low originality score has to do with the fact that it's fan art, so while this composition and style are all your own, it's still someone else's character (not a bad thing, just something to mark down for the purpose of the "Originality" moniker!)
I love him... for him being evil and cool ,not as for many of his fangirls love him (puppy eyes! so cute! bloeh, I hate this...) I'm also planning on a picture of him, since I saw the Avengers movie the first time