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