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