A contraction of the word complement and the American slang form of disrespect (diss), a complediss is a backhanded comment. It could be a complement followed by a criticism (or vice versa), as well as a criticism shrouded under the pretext of a complement.
A complediss in which a complement is followed by a criticism: I thought that your performance was very good, It would be great though if you would liven it up more, because it wasn't exactly teeming with energy.
A complediss in which a complement is actually a diss : That's really cool how that watch makes your arm budge on both sides. I wish my arm was big enough to do that.