Here is the full list of all 50 Divinity: Original Sin 2 - there are Definitive Edition achievements worth 1,000 gamerscore.
Escape the kraken's clutches
Flee Fort Joy for good
Remove your Source Collar
Defeat Alexandar in Fort Joy
Escort the Black Cat out of Fort Joy
Force Dallis to retreat from combat in Fort Joy
Kill Radeka
Take command of the Lady Vengeance
Escape Dallis' siege on the Lady Vengeance without killing every minion
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
Unlock your second Source Point slot
Unlock your third Source Point slot
Awaken the corrupted Ancestor Tree on Bloodmoon Island
Correctly answer all of Crispin's questions
Lockpick your way into Mordus' hidden lair
Obtain Anathema
Free Saheila 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
Enter the Academy
Kill a God
Convince all party members to let you ascend
Discover the hidden entrance to the Academy
Become The One arena champion
Craft the Swornbreaker
Swear to the Covenant
Successfully walk the Path of Blood
Ascend to Divinity
Share Source with all of Rivellon
Purge Rivellon of all Source
Share Divinity with the Doctor
Persuade Toyseller Sanders to give you his amulet
Rescue Arhu
Defeat Adramahlihk
Complete the game in Explorer Mode
Complete the game in Classic Mode
Complete the game in Tactician Mode
Complete the game in Honour Mode
Complete the game in Story Mode
Become champion of the Fort Joy arena