The Halo 3: ODST Add-on for Halo: The Master Chief Collection has 99 achievements.
H3: ODST: Kill 10 Engineers.
H3: ODST: Kill 25 Engineers.
H3: ODST: Find the 1st Audio Log.
H3: ODST: Find the 2nd Audio Log.
H3: ODST: Find the 3rd Audio Log.
H3: ODST: Find the 4th Audio Log.
H3: ODST: Find the 5th Audio Log.
H3: ODST: Find the 6th Audio Log.
H3: ODST: Find the 7th Audio Log.
H3: ODST: Find the 8th Audio Log.
H3: ODST: Find the 9th Audio Log.
H3: ODST: Find the 10th Audio Log.
H3: ODST: Find the 11th Audio Log.
H3: ODST: Find the 12th Audio Log.
H3: ODST: Find the 13th Audio Log.
H3: ODST: Find the 14th Audio Log.
H3: ODST: Find the 15th Audio Log.
H3: ODST: Find the 16th Audio Log.
H3: ODST: Find the 17th Audio Log.
H3: ODST: Find the 18th Audio Log.
H3: ODST: Find the 19th Audio Log.
H3: ODST: Find the 20th Audio Log.
H3: ODST: Find the 21st Audio Log.
H3: ODST: Find the 22nd Audio Log.
H3: ODST: Find the 23rd Audio Log.
H3: ODST: Find the 24th Audio Log.
H3: ODST: Find the 25th Audio Log.
H3: ODST: Find the 26th Audio Log.
H3: ODST: Find the 27th Audio Log.
H3: ODST: Find the 28th Audio Log.
H3: ODST: Find the 29th Audio Log.
H3: ODST: Find the 30th Audio Log.
H3: ODST: Complete every level of the game on Easy difficulty.
H3: ODST: Complete every level of the game on Normal difficulty.
H3: ODST: Complete every level of the game on Heroic difficulty.
H3: ODST: Complete every level of the game on Legendary difficulty.
H3: ODST: Find the 1st clue to unraveling the mystery.
H3: ODST: Find the 2nd clue to unraveling the mystery.
H3: ODST: Find the 3rd clue unraveling the mystery.
H3: ODST: Find the 4th clue unraveling the mystery.
H3: ODST: Find the 5th clue unraveling the mystery.
H3: ODST: Find the 6th clue unraveling the mystery.
H3: ODST: Find all 30 Audio Logs.
H3: ODST: Complete Tayari Plaza.
H3: ODST: Complete Uplift Reserve.
H3: ODST: Complete Kizingo Blvd.
H3: ODST: Complete ONI Alpha Site.
H3: ODST: Complete NMPD HQ.
H3: ODST: Complete Kikowani Station.
H3: ODST: Complete Data Hive.
H3: ODST: Complete Coastal Highway.
H3: ODST: Beat the par time on Tayari Plaza.
H3: ODST: Beat the par time on Uplift Reserve.
H3: ODST: Beat the par time on Kizingo Blvd.
H3: ODST: Beat the par time on ONI Alpha Site.
H3: ODST: Beat the par time on NMPD HQ.
H3: ODST: Beat the par time on Kikowani Station.
H3: ODST: Beat the par time on Data Hive.
H3: ODST: Beat the par time on Coastal Highway.
H3: ODST: Beat par time on all Halo 3: ODST levels.
H3: ODST: Beat the par score on Tayari Plaza.
H3: ODST: Beat the par score on Uplift Reserve.
H3: ODST: Beat the par score on Kizingo Blvd.
H3: ODST: Beat the par score on ONI Alpha Site.
H3: ODST: Beat the par score on NMPD HQ.
H3: ODST: Beat the par score on Kikowani Station.
H3: ODST: Beat the par score on Data Hive.
H3: ODST: Beat the par score on Coastal Highway.
H3: ODST: Beat par score on all Halo 3: ODST levels.
H3: ODST: Complete Coastal Highway on 4-player Legendary co-op, with Iron, and no 'Hog or Scorpion.
H3: ODST: Complete a Halo 3: ODST LASO Campaign playlist.
H3: ODST: Complete three Halo 3: ODST playlists.
H3: ODST: Complete a Halo 3: ODST playlist.
H3: ODST: Complete all Halo 3: ODST Legendary campaign missions in under 3 hours.
H3: ODST: View the missing link.
H3: ODST: Find a legendary hidden music cue.
H3: ODST: Face it.
H3: ODST: Is there a toy inside?
H3: ODST: Finish any level solo on Legendary, with no shots fired or grenades thrown.
H3: ODST: Kill 5 sleeping Grunts on Mombasa Streets.
H3: ODST: Assassinate 3 Brutes in a row on Data Hive.
H3: ODST: Kill 4 enemies with a single plasma or frag grenade.
H3: ODST: Kill 3 Jetpack Brutes with a shotgun on Oni Alpha Site.
H3: ODST: Destroy a Wraith…with your bare hands.
H3: ODST: Kill a Drone with a flame grenade on Data Hive.
H3: ODST: Swap Dare's pistol for a Rocket Launcher on Coastal Highway.
H3: ODST: Complete any level without using a health pack on Heroic or Legendary.
H3: ODST: Complete any level without dying on Heroic or Legendary.
H3: ODST: Complete any level without activating VISR mode.
H3: ODST: Finish Tayari Plaza with at least one Marine still breathing.
H3: ODST: Complete NMPD HQ without firing the Sniper Rifle on Heroic or Legendary.
H3: ODST: Splatter 7 enemies with a Banshee on Kikowani Station.
H3: ODST: Pilot a Banshee on Kizingo Boulevard.
H3: ODST: Destroy 5 Phantoms on NMPD HQ.
H3: ODST: Destroy 7 Wraiths on Oni Alpha Site.
H3: ODST: I've got my eye on you, Marine.
H3: ODST: Complete any level without using Covenant weapons.
H3: ODST: Play a game of Halo 3: ODST on the 22nd of any month.
H3: ODST: Earn a Triple Kill medal with the pistol on any level.