Full list of all 58 Halo Wars achievements worth 1,200 gamerscore. It takes around 80-100 hours to unlock all of the achievements in the base game on Xbox 360.
The base game contains 50 achievements worth 1,000 Gamerscore, and there are 2 DLC packs containing 8 achievements worth 200 Gamerscore.
Achievements they've won
Achievements they've not won
Obtain the General Rank on Xbox LIVE
Finish all missions under Par Time on Heroic difficulty
Get a Gold Medal on every Campaign Mission
Complete the Campaign on Legendary Difficulty
Complete the Campaign on Heroic Difficulty
Complete entire Campaign in Co-op Mode
Get 20,000 points in any Skirmish Game
Obtain the Lieutenant Rank on Xbox LIVE
Win and have the Highest Score in a Matchmade Skirmish Game on Xbox LIVE
Play Halo Wars for at least 24 Total Hours
Win a Matchmade Skirmish Game on Xbox LIVE
Obtain a Lifetime Campaign Score over 1,000,000
Win a game on every Skirmish Map
Unlock All Timeline Events
Win a 3v3 Skirmish game with 2 AI Allies
Win a Skirmish Game with every Leader
Get a winning High Score with 10 or less Squads against the Heroic AI
Win a Heroic Skirmish Game against the AI in under 10 minutes
Win a game in every Skirmish Game Mode
Use one of the 6 Major Leader Powers to destroy an enemy's last unit
Mission 1: Ram 50 Grunts with Warthogs
Mission 8: Use Elephants to train 100 Infantry
Mission 11: Save all the Airlocks
Mission 12: Repair the Power Core in less than 4 minutes
Get a Gold Medal with all Debuff Skulls Active
Improve your Score in any Campaign Mission
Completed Act IV on any difficulty
Mission 15: Open the Doors in order
Collect all Skulls
Unlock 20 Timeline Events
Mission 14: Don't claim an extra base
Mission 13: Destroy 25 units with the Scarab
Completed Act III on any difficulty
Mission 7: Do not destroy any Power Node
Mission 6: Successfully protect every Rhino
Mission 4: Save Adam
Mission 5: Jack 6 Covenant Vehicles
Mission 2: Destroy every Methane Tank
Mission 10: Disrupt all Tractor Beams
Mission 9: Put every Colony in Hibernation Mode at the same time
Completed Act II on any difficulty
Collect your first Skull
Complete any Campaign Mission in Co-op Mode
Get a Gold Medal on any mission
Obtain the Recruit Rank on Xbox LIVE
Win a Skirmish Game with Dual Scarabs
Completed Act I on any difficulty
Mission 3: Kill at least 5 Covenant Units with the Bridge
Completed Mission 1 on any difficulty
Get a Scarab during a Reinforcement game.
Gain at least 15 population from a single wave in a Reinforcement game.
Win and never trail in a Tug of War game.
Score the winning point in a game of Keepaway against Legendary AIs.
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.
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.