What is so bad about this picture. . .

[Kirito]

you need to work on your shading and coloring, also, proportions are fine lengthwise, but thickness could use a little work, it seems that it's trying to be skinny, and then it's trying to be muscular at the same time, ti just looks off. It's a good start, much better than what I can produce, but you wanted honesty here. The lines are in places to straight, the curvature just isn't right. Despite your lines, your shading is what could use the most work. Also, the waist looks a little on the thin side, but I'd have to see comparative work. It's too straight. That said, it's still good work, it just needs some refinement.