Only nitpickery I have is that Unicron's sheer gravity should be strong enough to shear Earth to shreds. After that I must applaud your skill of getting so many details without losing main focus. It even looks contemplating about its existence.
Are you talking about the IDW comic. He is the same size there as he is in this picture when he transformed to robot mode. Here he is about 5-6 times the size of Earth. Cybertron in the Unircon comic was twice the size of Earth. Unicron in Robot mode is about 1/2 to 2/3 the size of Jupiter which he flies through in issue 4. Any time you would see Unicron from Earth's surface he was actually not right up close to the planet, but due to a matter of perspective would look very close due to his size. If you are talking about how he looked in the last issue, I didn't get to work on all of it, so the other artist might not have made the scale the same as I had planed out.
And thank you so much for posting this. I was never able to find more than a small cropped version of this image to really stare at, so when I saw this full version at last, I was properly floored. It's SO. GOOD. I absolutely LOVE the way you designed the accumulated planet-shell bits all over him.
And full marks to sebastiancheng as well for those Gorgeous colors!!!