Unicron is the biggest enemy of Transformers: Prime. Before the dawn of time, he is known as the bringer of chaos, lord of the undead and one of the main sources of evil in the entire universe and the very source of Dark Energon itself.
He also happens to be Earth, the planet itself formed around him over billions of years....he is waking up from his slumber.
LOL. I thought it was a typo. My bad.
I never met the guy. ;-)