Here is the full list of all 97 Divinity: Original Sin 2 achievements. It takes around 200 hours to unlock all of the achievements on Windows.
Become champion of the Fort Joy arena
Gain the Hero tag
Arrive at Reaper's Eye
Escape the kraken's clutches
Perform a successful theft
Flee Fort Joy for good
Remove your Source Collar
Face a higher power
Arrive at the Sanctuary of Amadia
Rescue Gareth from Braccus' Armoury
Defeat Alexandar in Fort Joy
Escort the Black Cat out of Fort Joy
Force Dallis to retreat from combat in Fort Joy
Kill Slane
Kill Radeka
Take command of the Lady Vengeance
Welcome Tarquin to the Seekers' service
Escape Dallis' siege on the Lady Vengeance without killing every minion
Enter the Hall of Echoes
Escape Dallis' siege on the Lady Vengeance after killing every minion
Arrive at Reaper's Coast
Meet Meistr Siva
Become champion of the Driftwood Arena
Use your first Source Skill
Unlock your second Source Point slot
Unlock your third Source Point slot
Set Gareth on a path of vengeance
Set Gareth on a path of reconciliation
Learn of the Council of Seven's location from a higher power
Learn of the Council of Seven's location from Malady
Learn of the Council of Seven's location from The Advocate
Awaken the corrupted Ancestor Tree on Bloodmoon Island
Correctly answer all of Crispin's questions
Lockpick your way into Mordus' hidden lair
Obtain Anathema
Escort Saheila outside without fighting the Lone Wolves
Take the ferry to Bloodmoon Island
Tame Featherfall
Help free Mari from the Voidwoken
Kill Andras, the necromantic dog
Perform successful surgery on Natalie
Destroy every Voidwoken egg in Reaper's Cove
Serve Garvan the tainted stew
Receive Dorotya's kiss
Adopt Peeper
Arrive at the Nameless Isle
Enter the Academy
Enter The Arena of the One
Pray at every altar on the Nameless Isle
Convince Alexandar to ally with you
Convince all party members to let you ascend
Discover the hidden entrance to the Academy
Swear to the Covenant
Arrive at Arx
Gain entrance to Lucian's Crypt without following the Path of Blood
Successfully walk the Path of Blood
Defeated the Kraken
Ascend to Divinity
Share Source with all of Rivellon
Purge Rivellon of all Source
Submit to the God King
Share Divinity with The Doctor
The Red Prince: Kill the Red Princess
The Red Prince: Become the father of dragons
Lohse: Embrace your demon
Lohse: Banish your demon
Sebille: Serve the Mother Tree
Sebille: Destroy the Mother Tree
Fane: Return the Eternals to Rivellon
Fane: Embrace this strange new world
Ifan: Kill Lucian
Ifan: Forgive Lucian
Beast: Assassinate the Queen
Persuade Toyseller Sanders to give you his amulet
Discover Reimond's Lair
Rescue Arhu
Defeat Adramahlihk
Make a deal with Adramahlihk
Beast: Ally with the Queen
Shapeshift into every race
Complete the game in Explorer Mode
Complete the game in Classic Mode
Complete the game in Tactician Mode
Craft a scroll
Kill an enemy using Teleportation
Craft a skill
Equip runes to all of an item's available slots
Speak to an animal's spirit
Use the Curse skill
Gain the Villain tag
Win a persuasion event
Craft a grenade
Get caught breaking the law
Successfully begin a match in Arena Mode
Successfully begin a Game Master session
Complete the game in Honour Mode
Sebille: Kill the Master