10 Best Star Trek Villains In Only One Episode
1. The Planet Killer - The Original Series, The Doomsday Machine
The Great Slug in Space, this entity was frightening people long before the Borg or Species 8472 ever came along. This merciless, voiceless killer was hell bent on eating the universe, one planet at a time, with seemingly no way to stop it.
In one of the greater shocks of the Original Series, the Enterprise discovers the severely damaged remains of its sister ship, the USS Constellation. It was one of the first examples of seeing what was effectively the Enterprise herself broken to the point of destruction. The maddened Commodore Decker is brought aboard. The episode quickly becomes a thinly veiled retelling of Moby Dick.
The Planet Killer is the White Whale. Decker is Ahab. His quest for vengeance against the creature that destroyed his crew drags him to insanity, though threatens to bring the Enterprise with him. His eventual demise seems almost pointless - he pilots a shuttle into the gaping maw of the creature, dying in a blaze. His death does give Spock and idea, who encourages the Constellation to also be flown into the mouth of the creature.
The Doomsday Machine remains one of the Original Series' most popular episodes and The Planet Killer is a truly frightening adversary. There is no crew or captain to convince - it simply devours and there is no way to reason with it. And it is a great help to the creature that the music in the episode is evocative of the Jaws theme.