Full list of all 700 Halo: The Master Chief Collection achievements worth 7,000 gamerscore.
The base game contains 400 achievements worth 4,000 Gamerscore, and there are 6 DLC packs containing 300 achievements worth 3,000 Gamerscore.
Halo CE: Complete The Truth and Reconciliation with at least four rounds left in your Sniper Rifle.