Oh lawd the effects her are luff~
Well that and the grungy background.

Well here's my crit. Apologies if I sound rude/harsh/etc and apologies if you didn't like the fact I redlined it.

Colorwise:

Though I seem to find it that not all of Venom should be dark (cause of the glow from her finger making a light source).
But lighting wise. Normally with glows and stuff some light is reflected and can sometimes change colors on some thing (in the case add a greenish hue on some parts from the light).
For both there seems to also be an indefinite light source for both of them (the highlights) I'm not too sure where its from but I'm assuming its from their finger glows.

Anatomy wise:

Duke's left hand is wonky (don't know how to explain it but I corrected it in the red lines). Also his right arm seemed shorter than his left. Duke's (hair?) also seems very stiff and should have more of a "flow".
Venom's feet are also weird since her right foot should be looked from the back but in the pic gave a bit of a side-back view. The angle for her left foot is correct but it didn't come out very well Also by the angle the part of Vemon's left...err.. boob shouldn't be showing.
Redlines: [link]