He's Unstoppable!

He’s Unstoppable! is an achievement in Halo: Combat Evolved Anniversary. It is awarded for completing any level on either Heroic or Legendary difficulty without taking any damage to the player's health.

It is represented by the Legendary difficulty icon with a symbol of a white cross inside a red hexagon on the Sangheili skull.

Trivia
The name of this achievement is a direct quote from an Unggoy in Halo: Combat Evolved when the player, as John-117, kills most of the said Unggoy's allies.