I don't think there is really a lack of lighting here, I believe the chosen background makes the scene seem a bit darker than it really is. Also the shadows from the position of the lighting feed the sensation. However were the scene any more brightly lit, the hair and the yellow in the chest would start to lose detail. Perhaps a lighter background and a lighting direction that casts less shadow could help here.
Focus/depth of field is very good. Color saturation and balance are very good also.
Is the red on the Troll's right hand supposed to represent blood? If so, it is almost un-noticeable. Perhaps more blood would have worked here. Or none... As it is the red splotch is a question mark that doesn't really detract, but at the same time doesn't really add to the image either.
As someone else noted, the elephant is a bit small to really imply the troll is being squashed. However, overall it is a cute/humorous image.
Pretty funny. Your focus and clarity are ok, the angle is ok, but the cropping is too close. you cut off the hair, and the elephants butt. I would like to have seen the whole picture. The colors are good. I think that the background works, nothing distracting there. Good luck in the challenge.