you have this kind of cartoony stock of the hulk, and some nice effects, and the realistic trees in the background clash with them. i would change the bg
It's really not the BG guys, its just the colouring of the effects that makes it look like three seperate lates [bg - effects - render] The tree's could fit fine.
Change the color of the effects c4d's to a more suiting color. I always do it with a clipping masked adjustment layer .