@Parody Put this image as your background, go to Edit>Transform>Flip Horizontally (not neccessary, but I think it'd look better), put the render on the background, softly erase edges from render to make better blending, put a matching gradient (choose a colour from the background/render that is most common) and then put some C4D or smudge or whatever the shit you want to do with it.
P.S. That part of the clipped brush near his neck looks like smudged/blurred, fix that. And please give me the link of the original render. Thanks in advance.