This achievement can be unlocked by loading up Chapter VIII To The Core on the checkpoint "Divide and Conquer". After killing off a few spiders and Decepticons, you activate a switch and walk onto a side-bridge. Look to your left and you see a great mechanical slug sliming along a bridge. Ahead of him is a Decepticon Demolisher. You should also see a massive stalactite encrusted with dark energon crystals hanging above the bridge. Shoot this to crush the Decepticon and rescue the gastropod android from his untimely death.