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