Here is the full list of all 75 Halo Wars: Definitive Edition achievements worth 1,500 gamerscore.
Won 100 Skirmish or Multiplayer Matches.
Won a Public game.
Won and had the highest score in a Public Game.
Won 75 Skirmish or Multiplayer Matches.
Won 50 Skirmish or Multiplayer Matches.
Won 40 Skirmish or Multiplayer Matches.
Won 30 Skirmish or Multiplayer Matches
Mission 10: Distrupted all Tractor Beams.
Won a game on every Skirmish Map.
Hot dropped 50 squads to your Covenant Leader in a single game on Barrens.
Got a Gold Medal with all Debuff Skulls Active.
Got a Scarab during a Reinforcement game.
Gained at Least 15 population from a single wave in a Reinforcement game.
Finished five missions under Par Time on Heroic difficulty.
Unlocked All Timeline Events.
Won 20 Skirmish or Multiplayer Matches
Mission 14: Didn't claim an extra base.
Finished one mission under Par Time on Heroic difficulty.
Collected all Skulls.
Obtained a lifetime campaign Score over 1,000,000.
Mission 4: Saved Adam.
Collected 8 Skulls.
Improved your Score in any Campaign Mission.
Won 10 Skirmish or Multiplayer Matches
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.
Completed Mission 14 on any difficulty.
Completed Mission 15 on any difficulty.
Mission 15: Opened the Doors in order.
Won a Skirmish Game with every Leader.
Won a game in every Skirmish Game Mode.
Unlock 20 Timeline Events.
Used one of the 6 Major Leader Powers to destroy an enemy's last unit.
Won and never trailed in a Tug of War game.
Won a Skirmish Game with Dual Scarabs.
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 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.
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.
Completed Mission 6 on any difficulty.
Mission 6: Successfully protected every Rhino.
Collected your first Skull.
Completed Mission 5 on any difficulty.
Mission 5: Jacked 6 Covenant Vehicles.
Completed Mission 4 on any difficulty.
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.
Unlocked a Timeline Event.
Got a Gold Medal on any mission.
Completed Mission 1 on any difficulty.
Complete the Campaign on Heroic Difficulty.
Complete the Campaign on Legendary Difficulty.
Finish all missions under Par Time on Heroic difficulty.
Get a Gold Medal on every Campaign Mission.
Mission 1: Ram and kill 50 Grunts with Warthogs.
Mission 7: Do not destroy any Power Node.
Score the winning point in a game of Keepaway against Legendary AI's.
Complete any Campaign Mission in Co-op Mode.
Get 20,000 points in any Skirmish Game.
100% Completion.
Play Halo Wars for at least 24 Total hours.
Disrupt 5 active Leader Powers in a single game on Blood River.