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