Transformers: War for Cybertron

Guide above by DiatomicMaster is dead on, but if you have already played the level and skipped over the cheevo, load up Chapter 3, Iacon Destroyed, checkpoint The Stellar Galleries. It will load you right into the room where the planets are circling the Cybertron. You will know when you have destroyed all of the circling planets when Cybertron is taken over by Energon. The cheevo pops right after that.

In Iacon Destroyed of the Decepticon campaign, you'll come across a gallery room you must activate. A cinematic plays where Megatron converses with a holograph of Zeta Prime over the switch, if I recall.

At the center of this room is a very large model of Cybertron with planets circling it. After you've finished off all the Autobots, destroy every single black planet that is orbiting. Some are quite small, so be sure to get every one. Once you've hit every one, the achievement will pop.

Nice an easy to do ether first time round playing or returning to the level. Load up chapter III checkpoint Stellar galleries and shoot the planets surrounding cybertron, once you do an animation will play then achievement will pop.