Here is the full list of all 22 Absolver achievements.
Kill your opponent with his own weapon in 1v1
Kill all bosses in their last level with one character
Have Cargal kill Kilnor (or the opposite)
Become a disciple of your school
Kill 100 Players Character (Any Character)
Reach Gamemode Level 5
Win 1 PVP Duel
Join a school
Loot 1 weapon
Master 1 new Attack
Kill Kuretz
Kill Cargal & Kilnor
Kill Risryn
Kill all marked ones with one character
Become an Absolver
Push AI off ledge
Open all cairns with one character
Create a school
Unlock all fighting styles with one character
Master all attacks with one character
Reach Gamemode Level 100