Well, what looks wrong with the torso?
If you are refering to the curvature of the spine, then I will have to explain something about action lines. Action lines are the basic structure or pose of the character. It comes from the head and ends at the feet. So what I was trying to do here was create a lax, cool character. So, the spine is bending like ")" to show he is relaxed. If I had pixeled the whole body, the action line would be a bit of an "S". Hope this clears things up.