After watching Transformers Prime all over again, I started to focus on the design of the Terrorcons from the first few episodes. The large bulbous bodies and thickened lower limb parts contrasted wonderfully against the leaner upper limb parts. I also liked the hints of purple throughout that contrasted against the bland, metallic coloring of the bots themselves. I know in the series that it signified dark energon but I still like it so I used purple here.
This moc is basically built around that overal body style. The back was supposed to be more flat than it actually turned out but it creates a nice hunch which actually adds to the 'alien' look and the viewable tanks increase a robotic atmosphere but the moc appears more organic.
I'd say that this MOC came out quite well, but the one part where you didn't stick to the aesthetic, the upper arms, look a little off. I'd suggest lengthening them slightly, so as to make the distinction between the shoulders and the actual arms a little clearer.