planet killer

Star Trek: The Original Series
Episode: TOS 035 - Doomsday Machine

This giant vessel is actually more of a spacefaring weapon, and made its way through our galaxy annihilating multiple planets and civilizations. The "doomsday machine" was destroyed by James T. Kirk in 2267. It is theorized that the ship was built by a long-gone civilization from another galaxy for use during an unknown war.