Wow, first off wonderful job. Love the dark hedgehogs as a whole, but then who does not like a badass.
Anyway, on to the critique proper. Love the styling of the poster, though it would have been nice to have seen the edges of the paper cut into the image as i can see and guess that his foot, and part of the whips are hanging off. Next the size of thorns on the left handed whip seem off, like they do not get smaller at the height of the arch correctly, but that might just be me. The shadow on his top spine seems a little off, but it is really hard to see, and does not impact the art much if at all.
Other then that, I look forward to seeing more of your art in the coming year.