Your Heresy Will Stay Your Feet Achievement in Halo: The Master Chief Collection

This achievement must be done on the Normal difficulty (or higher).

After destroying the first anti-air turret and crossing a bridge toward the mining facility, you will eventually turn down a walkway and enter an open courtyard infested with Covenant forces. In this area, typically directly ahead on the opposite raised walkway, is an Elite Zealot; the game will notify you of his presence with a red marker above his head, as well as an audio cue from your allies. You'll have to be quick in eliminating the Elite Zealot in order to unlock the achievement, so, regardless of difficulty, hit him with the Noob Combo (Plasma Pistol + DMR or Needle Rifle) to dispose of him quickly. If he does not die by your hand, or manages to escape, restart your checkpoint and try again.