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