Here is the full list of all 75 Halo Wars: Definitive Edition achievements worth 1,500 gamerscore.
Completed the Campaign on Legendary Difficulty.
Played Halo Wars for at least 24 Total hours.
Finished all missions under Par Time on Heroic difficulty.
Completed the Campaign on Heroic Difficulty.
Disrupted 5 active Leader Powers in a single game on Blood River.
Won a Public game.
Won and had the highest score in a Public Game.
Finished five missions under Par Time on Heroic difficulty.
Mission 1: Rammed and killed 50 Grunts with Warthogs.
100% Completion.
Got a Gold Medal on every Campaign Mission.
Won 100 Skirmish or Multiplayer Matches.
Won 75 Skirmish or Multiplayer Matches.
Killed 20 enemy squads with a continuous Covenant Leader Power on Memorial Basin.
Got 20,000 points in any Skirmish Game.
Finished one mission under Par Time on Heroic difficulty.
Collected all Skulls.
Got a Gold Medal with all Debuff Skulls Active.
Obtained a lifetime campaign Score over 1,000,000.
Mission 7: Did not destroy any Power Node.
Unlocked All Timeline Events.
Mission 2: Destroyed every Methane Tank.
Completed Mission 15 on any difficulty.
Mission 15: Opened the Doors in order.
Completed Mission 14 on any difficulty.
Mission 14: Didn't claim an extra base.
Completed Mission 13 on any difficulty.
Mission 13: Destroyed 25 units with the Scarab.
Mission 12: Repaired the Power Core in less than 4 minutes.
Completed Mission 12 on any difficulty.
Completed Mission 11 on any difficulty.
Mission 11: Saved all the Airlocks.
Completed Mission 10 on any difficulty.
Collected 8 Skulls.
Mission 10: Distrupted all Tractor Beams.
Completed Mission 9 on any difficulty.
Mission 9: Every Colony put in Hibernation Mode at the same time.
Completed Mission 8 on any difficulty.
Mission 8: Used Elephants to train 100 infantry.
Completed Mission 7 on any difficulty.
Finished with 5000 net resources tributed to your teammates on Memorial Basin except in Deathmatch.
Completed any Campaign Mission in Co-op Mode.
Completed Mission 6 on any difficulty.
Mission 6: Successfully protected every Rhino.
Completed Mission 5 on any difficulty.
Mission 5: Jacked 6 Covenant Vehicles.
Completed Mission 4 on any difficulty.
Mission 4: Saved Adam.
Improved your Score in any Campaign Mission.
Mission 3: Killed at least 5 Covenant Units with the Bridge.
Completed Mission 3 on any difficulty.
Won 50 Skirmish or Multiplayer Matches.
Won 40 Skirmish or Multiplayer Matches.
Won 30 Skirmish or Multiplayer Matches
Won a game on every Skirmish Map.
Won 20 Skirmish or Multiplayer Matches
Unlock 20 Timeline Events.
Won a game in every Skirmish Game Mode.
Won a 3v3 Skirmish game with 2 AI Allies.
Hot dropped 50 squads to your Covenant Leader in a single game on Barrens.
Got a Scarab during a Reinforcement game.
Gained at Least 15 population from a single wave in a Reinforcement game.
Won and never trailed in a Tug of War game.
Won 10 Skirmish or Multiplayer Matches
Scored the winning point in a game of Keepaway against Legendary AI's.
Won a Skirmish Game with Dual Scarabs.
Won a Skirmish Game with every Leader.
Used one of the 6 Major Leader Powers to destroy an enemy's last unit.
Got a winning High Score with 10 or less Squads against the Heroic AI.
Won a Heroic Skirmish Game against the AI in under 10 minutes.
Completed Mission 2 on any difficulty.
Collected your first Skull.
Unlocked a Timeline Event.
Got a Gold Medal on any mission.
Completed Mission 1 on any difficulty.