Here is the full list of all 75 Halo Wars: Definitive Edition achievements.
Get 20,000 points in any Skirmish Game.
100% Completion.
Finish all missions under Par Time on Heroic difficulty.
Get a Gold Medal on every Campaign Mission.
Win 100 Skirmish or Multiplayer Matches.
Win 75 Skirmish or Multiplayer Matches.
Disrupt 5 active Leader Powers in a single game on Blood River.
Complete any Campaign Mission in Co-op Mode.
Kill 20 enemy squads with a continuous Covenant Leader Power on Memorial Basin.
Win 50 Skirmish or Multiplayer Matches.
Obtain a lifetime campaign Score over 1,000,000.
Mission 5: Jack 6 Covenant Vehicles.
Get a Gold Medal with all Debuff Skulls Active.
Mission 1: Ram and kill 50 Grunts with Warthogs.
Collect all Skulls.
Unlock All Timeline Events.
Mission 14: Don't claim an extra base.
Mission 13: Destroy 25 units with the Scarab.
Mission 12: Repair the Power Core in less than 4 minutes.
Mission 11: Save all the Airlocks.
Mission 10: Distrupt all Tractor Beams.
Play Halo Wars for at least 24 Total hours.
Mission 9: Put every Colony in Hibernation Mode at the same time.
Mission 8: Use Elephants to train 100 infantry.
Mission 7: Do not destroy any Power Node.
Mission 6: Successfully protect every Rhino.
Mission 3: Kill at least 5 Covenant Units with the Bridge.
Mission 2: Destroy every Methane Tank.
Win 40 Skirmish or Multiplayer Matches.
Win 30 Skirmish or Multiplayer Matches
Hot drop 50 squads to your Covenant Leader in a single game on Barrens.
Get a Scarab during a Reinforcement game.
Gain at Least 15 population from a single wave in a Reinforcement game.
Win and never trail in a Tug of War game.
Win a game on every Skirmish Map.
Win 20 Skirmish or Multiplayer Matches
Use one of the 6 Major Leader Powers to destroy an enemy's last unit.
Win a game in every Skirmish Game Mode.
Win a Heroic Skirmish Game against the AI in under 10 minutes.
Get a winning High Score with 10 or less Squads against the Heroic AI.
Score the winning point in a game of Keepaway against Legendary AI's.
Finish with 5000 net resources tributed to your teammates on Memorial Basin except in Deathmatch.
Win 10 Skirmish or Multiplayer Matches
Improve your Score in any Campaign Mission.
Complete the Campaign on Heroic Difficulty.
Complete the Campaign on Legendary Difficulty.
Completed Mission 15 on any difficulty.
Mission 15: Open the Doors in order.
Completed Mission 14 on any difficulty.
Win a Skirmish Game with every Leader.
Win a Skirmish Game with Dual Scarabs.
Unlock 20 Timeline Events.
Completed Mission 13 on any difficulty.
Completed Mission 12 on any difficulty.
Completed Mission 11 on any difficulty.
Win a Public game.
Win and have the highest score in a Public Game.
Win a 3v3 Skirmish game with 2 AI Allies.
Finish five missions under Par Time on Heroic difficulty.
Completed Mission 10 on any difficulty.
Collect 8 Skulls.
Completed Mission 9 on any difficulty.
Get a Gold Medal on any mission.
Completed Mission 8 on any difficulty.
Completed Mission 7 on any difficulty.
Completed Mission 6 on any difficulty.
Completed Mission 5 on any difficulty.
Completed Mission 4 on any difficulty.
Finish one mission under Par Time on Heroic difficulty.
Mission 4: Save Adam.
Completed Mission 3 on any difficulty.
Completed Mission 2 on any difficulty.
Collect your first Skull.
Completed Mission 1 on any difficulty.
Unlock a Timeline Event.