Metroid unit 318 was a Tallon Metroid briefly mentioned in Space Pirate scan logs in Metroid Prime 2: Echoes. It defied commands from the Space Pirates and killed one of its handlers before it was put down.
"Termination Report 07.195.02
Metroid unit 318 was put down today after a failed domestication session. Metroid unit refused commands and terminated one of its handlers before it was subdued."