Vogon

The Vogons were a species of hostile creatures that were once a threat to Earth but were stopped by the Doctor.

The Fourth Doctor told the Hornets that they were not as much of a threat to the planet as the Vogons, Pescatons, Trods or Krynoids. (AUDIO: A Sting in the Tale)

Behind the scenes
The Vogons are a reference to The Hitchhiker's Guide to the Galaxy by Douglas Adams, where they actually successfully destroyed Earth.