Commuter
From Halopedia, the Halo wiki
Commuter is an achievement in Halo: The Master Chief Collection. It is unlocked by completing the level Metropolis on Heroic or Legendary without entering any vehicles. The achievement is worth 10 Gamerscore.
Tips
The achievement is made easy by utilizing the Scarab skull, which turns every gun the player uses into a Scarab Gun, and the Bandanna skull, which grants the player unlimited ammo. Players who find this method so easy as to be unsporting may choose to use the Bandanna skull alone and utilize unlimited rockets and sniper rounds.