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