I really like the way you drew this. The expression on Thor's face is clearly shown, giving this picture emotion. It is really hard to pull off emotions in a picture, and you did a good job of showing it. You can definitely tell there is tension between them.
I also like the shading of the picture. You did just the right amount and did not go overboard like some people do. You can tell it is a drawing, but it doesn't look cartoon like. You can clearly see the facial features on both Thor and Loki, giving it a nice effect. I also like the way you did the hair. Every strand looks individually drawn, and you did a good job with the lighting as well.