No missable achievements (plus 75 unknown)
Sign in with Steam or Xbox to track your progress, and:
Unlock a Timeline Event.
Get a Gold Medal on any mission.
Collect your first Skull.
Win a Public game.
Win a 3v3 Skirmish game with 2 AI Allies.
Win and have the highest score in a Public Game.
Use one of the 6 Major Leader Powers to destroy an enemy's last unit.
Mission 13: Destroy 25 units with the Scarab.
Mission 9: Put every Colony in Hibernation Mode at the same time.
Complete any Campaign Mission in Co-op Mode.
Finish one mission under Par Time on Heroic difficulty.
Win 10 Skirmish or Multiplayer Matches
Mission 11: Save all the Airlocks.
Mission 4: Save Adam.
Win a Skirmish Game with Dual Scarabs.
Mission 3: Kill at least 5 Covenant Units with the Bridge.
Improve your Score in any Campaign Mission.
Mission 15: Open the Doors in order.
Mission 6: Successfully protect every Rhino.
Unlock 20 Timeline Events.
Mission 10: Distrupt all Tractor Beams.
Win 20 Skirmish or Multiplayer Matches
Win a Skirmish Game with every Leader.
Finish five missions under Par Time on Heroic difficulty.
Collect 8 Skulls.
Play Halo Wars for at least 24 Total hours.
Mission 2: Destroy every Methane Tank.
Win 30 Skirmish or Multiplayer Matches
Win a Heroic Skirmish Game against the AI in under 10 minutes.
Gain at Least 15 population from a single wave in a Reinforcement game.
Get a winning High Score with 10 or less Squads against the Heroic AI.
Mission 5: Jack 6 Covenant Vehicles.
Win 40 Skirmish or Multiplayer Matches.
Complete the Campaign on Heroic Difficulty.
Obtain a lifetime campaign Score over 1,000,000.
Get 20,000 points in any Skirmish Game.
Win 50 Skirmish or Multiplayer Matches.
Mission 14: Don't claim an extra base.
Finish with 5000 net resources tributed to your teammates on Memorial Basin except in Deathmatch.
Win and never trail in a Tug of War game.
Get a Gold Medal on every Campaign Mission.
Collect all Skulls.
Win a game in every Skirmish Game Mode.
Mission 8: Use Elephants to train 100 infantry.
Complete the Campaign on Legendary Difficulty.
Mission 12: Repair the Power Core in less than 4 minutes.
Win 75 Skirmish or Multiplayer Matches.
Disrupt 5 active Leader Powers in a single game on Blood River.
Win a game on every Skirmish Map.
Mission 7: Do not destroy any Power Node.
Get a Scarab during a Reinforcement game.
Win 100 Skirmish or Multiplayer Matches.
Hot drop 50 squads to your Covenant Leader in a single game on Barrens.
Finish all missions under Par Time on Heroic difficulty.
Mission 1: Ram and kill 50 Grunts with Warthogs.
Score the winning point in a game of Keepaway against Legendary AI's.
Get a Gold Medal with all Debuff Skulls Active.
Unlock All Timeline Events.
Kill 20 enemy squads with a continuous Covenant Leader Power on Memorial Basin.