Full list of all 80 XCOM 2 achievements worth 1,520 gamerscore. It takes around 150-200 hours to unlock all of the achievements in the base game on Xbox One.
The base game contains 50 achievements worth 1,000 Gamerscore, and there are 3 DLC packs containing 30 achievements worth 520 Gamerscore.
Evacuated a soldier whose bleed-out timer was still running
Sold goods worth 1000 supplies to the Black Market
Built a facility in every Avenger slot
Built a radio relay on every continent
Gotten all of the continent bonuses available in a single campaign
Killed an enemy with a hacked turret
Overthrown the aliens at any difficulty level
Overthrown the aliens on Commander difficulty
Created the Commander's Avatar
Completely upgraded a beam weapon with superior grade weapon upgrades
Completed the Avatar Autopsy
Recovered the Psi Gate
Caused an enemy to fall to its death
Killed an Avatar
Killed 500 aliens
Killed a Sectopod on the same turn you encountered it (in Single Player)
Recovered the Forge Item
Sabotaged an alien facility
Built the Shadow Chamber
Built Resistance Comms
Killed a Berserker in melee combat
Upgraded a facility
Earned a second tier hack reward
Hacked a Sectopod
Applied a PCS upgrade to a soldier
Beat a Retaliation mission with 3 or less civilian deaths
Recovered the Blacksite Data
Caused an enemy to die in a vehicle explosion
Killed 3 enemies in a single turn, with a single soldier, without explosives
Recovered a Codex Brain
Killed a Viper who was strangling a squadmate
Skulljacked an ADVENT Officer
Made contact with a region
Built an experimental item in the Proving Grounds
Completed a successful ambush
Upgraded a weapon
Completed a Rumor
Killed a Sectoid who was mind controlling a squadmate
Completed the tactical tutorial
Overthrow the aliens on Legend difficulty
Beat the game on Commander+ difficulty by July 1st
Beat the final mission using only conventional gear
Beat the game on Commander+ difficulty without buying a Squad Size upgrade
Beat the game on Commander+ without losing a soldier
Play in a multiplayer match
Beat a mission on Commander+ with a squad of soldiers only of the same class (but not Rookie)
Kill an enemy with every heavy weapon in the game (doesn't have to be in the same game)
Beat a mission in June or later using only Rookies
Skulljack each different type of ADVENT soldier (does not have to be in same game)
Beat the game on Commander+ difficulty in Ironman mode
Killed an alien ruler the first time you encountered it
Purchased all of the final tier hunter weapons
Killed the Archon Ruler
Killed all three alien rulers in a single game
Killed an alien ruler while it attempted to escape
Killed the Berserker Ruler
Killed the Viper Ruler
Investigated the Abandoned Research Facility
Use all ruler armor abilities in a single mission
Use a ruler armor ability against an alien ruler
Defeated an Avatar with a SPARK unit
Hit three shots on a single turn with a SPARK unit after using its Overdrive ability
Promoted a SPARK unit to Champion rank
A SPARK unit survived a mission it started with less than half health
Outfited a SPARK unit with the highest tier weaponry and armor
Built a SPARK unit
Beat the Lost Towers mission
Defeated a robotic enemy with a SPARK unit
Killed an enemy primed Derelict MEC before it can self-destruct
Complete a mission with three or more SPARK units in the squad
Raised a Templar to maximum Focus level, spend it all, and reach the max again in a single mission
Formed a level 3 bond between two soldiers
Raised XCOM's influence with all three factions to High in a single game
Performed three offensive actions against the same target with a Skirmisher in a single turn
Permanently defeated one of the Chosen
Got four kills from Shadow mode with a Reaper in a single mission
Rescued a soldier who was captured by the Chosen
Completed the Lost and Abandoned mission
Get 15 Headshots against Lost in a single turn
Complete a mission with all Tired soldiers and no casualties