Earthquake was once a great warrior, an ambitious man who thought he could rebel against the Decepticons. Now he's a bit too dead to rebel against anything.
UK Comics continuity
Earthquake tried to rebel against the Decepticons and got himself caught. Given his choice of punishment, he opted for Trial By Combat, where he faced his former comrade Tornado. Despite apparently being able to "WARP THE VERY SURFACE OF CYBERTRON!" he didn't make it out alive. In fact, neither of them did.