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