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