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.
Completed every Mission of the game on Legendary difficulty.
Completed every Mission of the game by yourself on Legendary difficulty.
Completed The Breaking on Legendary difficulty without the entire fireteam dying.
Finished the 13th mission without losing the Scorpion on Legendary difficulty.
Completed Swords of Sanghelios co-op with both Mantises on Heroic difficulty.
Kept 6 miners alive at the elevator in Evacuation on Heroic difficulty.
Knocked two Hunters into the ocean during the Battle of Sunaion.
Helped the Elite General charge the hill in Osiris on Heroic difficulty.
Destroyed the Phantom at the Covenant camp in Reunion on Heroic difficulty.
Completed every Mission of the game on Heroic difficulty.
Completed every co-op Mission on Heroic difficulty.
Found and claimed all Intel.
Simultaneously destroyed 2 cores in Guardians on Heroic difficulty.
Simultaneously killed two Wardens in The Breaking on Heroic difficulty.
Escaped the doomed Kraken by jumping onto a Phaeton piloted by a Spartan.
Traversed the canyon without a Phaeton in Reunion on Heroic difficulty.
Finished Evacuation within 18:00 without dying on Heroic difficulty.
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.
Killed a Grunt and smashed a grate with a Ground Pound in Battle of Sunaion.
Found and claimed all Skulls.
Completed Enemy Lines without destroying a Kraken turret.
Simultaneously assassinated two Elites in Blue Team co-op.
Completed any co-op Mission on Heroic difficulty.
Destroyed 10 walls or floors in Swords of Sanghelios.
Completed any Mission with 3+ Skulls active on Heroic difficulty.
Killed an enemy that's had its armor repaired in Unconfirmed.
Completed Glassed without entering a vehicle.
Completed Glassed without any players using Smart-Link.
Completed 5 matchmade games of Strongholds.
Completed 5 matchmade games of Capture the Flag.
Completed every Mission of the game on Normal difficulty.
Completed Mission 15.
Used a Ground Pound on an exterior power core in Guardians on Heroic difficulty.
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 Breakout.
Completed Mission 6.
Completed Mission 5.
Completed Mission 4.
Completed Mission 3.
Qualified for a Competitive Skill Rating.
Completed 3 matchmade games of Warzone.
Won a match on all three original Warzone maps.
Completed 5 matchmade games of Slayer.
Spectated a game.
Killed a Legendary Boss in Warzone.
Called in a REQ that costs 5 Energy or more.
Completed Mission 2.
Escaped the Hunters in the lab and fought them in the hangar in Blue Team.
Completed Mission 1.
Found and claimed a Skull.
Commanded your team of Spartans in Osiris.
Found and claimed one piece of Intel.
Opened a Gold REQ Pack.
Created and saved a Custom Game.
Changed your Service Tag in the Spartan Hub.
Changed your Spartan's gear in the Spartan Hub.
Changed your Emblem 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 500,000 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.
Successfully completed 5 Warzone Firefight matches.
Completed a Warzone Firefight match on 6 unique maps.
Earned a Mythic Boss Takedown in a Warzone Firefight match.