|Vermivorous the Invincible|
Vermivorous the Invincible is a Varkid enemy that can only be encountered by evolving a Varkid from Larval stage to Supreme Badass stage. There is much speculation over how to do so reliably, but there is an accepted route of evolution.
 Finding Vermivorous
A good start for encountering this enemy is to make sure you are playing in or have beaten True Vault Hunter Mode.
Travel to an area frequented by Varkids, such as Tundra Express or Caustic Caverns. Find a group of Bandits or Threshers and lead them towards a group of Varkids. Injure a few of the Larval Varkids, but do not kill them. Wait for one of them to evolve into an Ultimate Badass and then kill the rest of the Varkids except for the Ultimate Badass. Let the Ultimate Badass attack the Bandits or Threshers until it kills one or two of them, and it should go into a Supreme Badass Pod, and evolve into Vermivorous the Invincible.
Vermivorous will be Level 53 or higher when encountered, so it may be best to challenge him in cooperative online play to enhance your chances of defeating him.