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