I dunno what crit do you require? Only on the rendering and comp or on the models as well?
Here’s both 
I think you’ve done a great job, the only thing I’d change would be the size of the serpent’s hands (please don’t confuse them with arms :)) so just the hands/fists about double the size.
As far as rendering, it’s all great as well except the skin shader of Thor. The serpent and the rest of the scene look somewhere between realistic and plastic which I like very much, so Thor could use some of that as well.
I’d leave the comp vertical but just repose the Thore a bit so he looks more powerful and less like he’s gonna fall down. I don’t find it quite attractive being horizontal, not with the same lighting anyways.
Just have in mind as much as you rotate the picture to the left less and less threatning the serpent becomes.
Any help? 
Keep up the outstanding work
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