Full list of all 73 Halo 5: Guardians achievements worth 1,250 gamerscore. It takes around 40-50 hours to unlock all of the achievements in the base game.
The base game contains 65 achievements worth 1,000 Gamerscore, and there are 2 DLC packs containing 8 achievements worth 250 Gamerscore.
Kept 6 miners alive at the elevator in Evacuation on Heroic difficulty.
Won a match on all three original Warzone maps.
Helped the Elite General charge the hill in Osiris on Heroic difficulty.
Completed every Mission of the game by yourself on Legendary difficulty.
Found and claimed all Skulls.
Found and claimed all Intel.
Finished Evacuation within 18:00 without dying on Heroic difficulty.
Escaped the doomed Kraken by jumping onto a Phaeton piloted by a Spartan.
Simultaneously assassinated two Elites in Blue Team co-op.
Teamed up in a vehicle to kill 30 enemies in Unconfirmed co-op.
Knocked two Hunters into the ocean during the Battle of Sunaion.
Completed any Mission with 3+ Skulls active on Heroic difficulty.
Escaped the Hunters in the lab and fought them in the hangar in Blue Team.
Completed 5 matchmade games of Capture the Flag.
Destroyed the Phantom at the Covenant camp in Reunion on Heroic difficulty.
Completed every Mission of the game on Legendary difficulty.
Completed every co-op Mission on Heroic difficulty.
Simultaneously destroyed 2 cores in Guardians on Heroic difficulty.
Completed The Breaking on Legendary difficulty without the entire fireteam dying.
Finished the 13th mission without losing the Scorpion on Legendary difficulty.
Killed a Grunt and smashed a grate with a Ground Pound in Battle of Sunaion.
Completed Enemy Lines without destroying a Kraken turret.
Completed Swords of Sanghelios co-op with both Mantises on Heroic difficulty.
Destroyed 10 walls or floors in Swords of Sanghelios.
Traversed the canyon without a Phaeton in Reunion on Heroic difficulty.
Created and saved a Custom Game.
Completed Glassed without entering a vehicle.
Completed Glassed without any players using Smart-Link.
Completed 5 matchmade games of Slayer.
Completed 5 matchmade games of Breakout.
Completed 5 matchmade games of Strongholds.
Found and claimed a Skull.
Spectated a game.
Completed every Mission of the game on Normal difficulty.
Completed every Mission of the game on Heroic difficulty.
Completed Mission 15.
Used a Ground Pound on an exterior power core in Guardians on Heroic difficulty.
Completed Mission 14.
Simultaneously killed two Wardens in The Breaking on Heroic difficulty.
Completed Mission 13.
Operated four different vehicles at once in Mission 13 on Heroic difficulty.
Completed Mission 12.
Completed Mission 11.
Completed any co-op Mission on Heroic difficulty.
Completed Mission 10.
Completed Mission 9.
Completed Mission 8.
Completed Mission 7.
Completed Mission 6.
Killed a Legendary Boss in Warzone.
Completed 3 matchmade games of Warzone.
Qualified for a Competitive Skill Rating.
Completed Mission 5.
Killed an enemy that's had its armor repaired in Unconfirmed.
Completed Mission 4.
Completed Mission 3.
Opened a Gold REQ Pack.
Called in a REQ that costs 5 Energy or more.
Completed Mission 2.
Completed Mission 1.
Found and claimed one piece of Intel.
Commanded your team of Spartans in Osiris.
Changed your Spartan's gear in the Spartan Hub.
Changed your Emblem in the Spartan Hub.
Changed your Service Tag in the Spartan Hub.
Completed a mission in Score Attack co-op, with all participants scoring at least 200,000 points.
Completed a mission in Score Attack with at least 10,000 points.
Reached 50,000 points in Score Attack with a Skull multiplier of x2 or higher.
Beat the par time of a mission in Score Attack.
Completed a mission in Score Attack with at least 500,000 points.
Completed a Warzone Firefight match on 6 unique maps.
Successfully completed 5 Warzone Firefight matches.
Earned a Mythic Boss Takedown in a Warzone Firefight match.