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