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