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.
Won a match on all three original Warzone maps.
Found and claimed a Skull.
Called in a REQ that costs 5 Energy or more.
Completed Mission 7.
Completed Mission 6.
Completed Mission 5.
Killed an enemy that's had its armor repaired in Unconfirmed.
Completed Mission 4.
Completed Mission 3.
Completed any co-op Mission on Heroic difficulty.
Opened a Gold REQ Pack.
Completed 3 matchmade games of Warzone.
Killed a Legendary Boss in Warzone.
Changed your Spartan's gear in the Spartan Hub.
Changed your Service Tag in the Spartan Hub.
Changed your Emblem in the Spartan Hub.
Completed Mission 2.
Completed Mission 1.
Commanded your team of Spartans in Osiris.
Found and claimed one piece of Intel.
Create and save a Custom Game.
Spectate a game.
Complete 5 matchmade games of Strongholds.
Complete 5 matchmade games of Breakout.
Complete 5 matchmade games of Capture the Flag.
Complete 5 matchmade games of Slayer.
Complete Mission 13.
Complete Mission 14.
Complete every Mission of the game on Normal difficulty.
Complete every Mission of the game on Heroic difficulty.
Complete every Mission of the game on Legendary difficulty.
Find and claim all Intel.
Finish Evacuation within 18:00 without dying on Heroic difficulty.
Find and claim all Skulls.
Help the Elite General charge the hill in Osiris on Heroic difficulty.
Escape the Hunters in the lab and fight them in the hangar in Blue Team.
Simultaneously assassinate two Elites in Blue Team co-op.
Complete Glassed without entering a vehicle.
Complete Glassed without any players using Smart-Link.
Team up in a vehicle to kill 30 enemies in Unconfirmed co-op.
Keep 6 miners alive at the elevator in Evacuation on Heroic difficulty.
Traverse the canyon without a Phaeton in Reunion on Heroic difficulty.
Destroy the Phantom at the Covenant camp in Reunion on Heroic difficulty.
Destroy 10 walls or floors in Swords of Sanghelios.
Complete Swords of Sanghelios co-op with both Mantises on Heroic difficulty.
Complete Enemy Lines without destroying a Kraken turret.
Escape the doomed Kraken by jumping onto a Phaeton piloted by a Spartan.
Kill a Grunt and smash a grate with a Ground Pound in Battle of Sunaion.
Knock two Hunters into the ocean during the Battle of Sunaion.
Finish the 13th mission without losing the Scorpion on Legendary difficulty.
Operate four different vehicles at once in Mission 13 on Heroic difficulty.
Complete The Breaking on Legendary difficulty without the entire fireteam dying.
Simultaneously kill two Wardens in The Breaking on Heroic difficulty.
Use a Ground Pound on an exterior power core in Guardians on Heroic difficulty.
Simultaneously destroy 2 cores in Guardians on Heroic difficulty.
Complete every Mission of the game by yourself on Legendary difficulty.
Complete every co-op Mission on Heroic difficulty.
Complete Mission 12.
Complete any Mission with 3+ Skulls active on Heroic difficulty.
Qualify for a Competitive Skill Rating.
Complete Mission 8.
Complete Mission 9.
Complete Mission 10.
Complete Mission 11.
Complete Mission 15.
Complete a mission in Score Attack with at least 10,000 points.
Reach 50,000 points in Score Attack with a Skull multiplier of x2 or higher.
Complete 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.
Complete 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.