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 a Sangheili skull.

Trivia
The name of this achievement is a direct quote made by Unggoy NPCs in Halo: Combat Evolved, when most of said Unggoy's allies are killed.