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