Here is the full list of all 48 Shadwen achievements. It takes around 12-15 hours to unlock all of the achievements on Windows.
Complete Level 2: The Solitary Killer
Kill all the guards in Level 2: The Solitary Killer
Complete Level 1: The Apple Tree
Complete Level 3: The Way to Rivendon
Complete Level 4: The Cliffside Fort
Complete Level 5: The Walls of Rivendon
Complete Level 6: Longwall Prison
Complete Level 7: Shortwall Barracks
Complete Level 8: The Roads of Lowerton
Complete Level 9: Lowerton Storages
Complete Level 10: Lowerton Worksite
Complete Level 11: Rivendon Harbour
Complete Level 12: The Streets of Rivendon
Complete Level 13: Rivendon Uptown
Complete Level 14: The Castle District
Kill all the guards in Level 3: The Way to Rivendon
Kill all the guards in Level 4: The Cliffside Fort
Kill all the guards in Level 5: The Walls of Rivendon
Kill all the guards in Level 6: Longwall Prison
Kill all the guards in Level 7: Shortwall Barracks
Kill all the guards in Level 8: The Roads of Lowerton
Kill all the guards in Level 9: Lowerton Storages
Kill all the guards in Level 10: Lowerton Worksite
Kill all the guards in Level 11: Rivendon Harbour
Kill all the guards in Level 12: The Streets of Rivendon
Kill all the guards in Level 13: Rivendon Uptown
Kill all the guards in Level 14: The Castle District
Kill all the guards in in Level 15: Rivendon Castle
Don't kill anyone in Level 2: The Solitary Killer
Don't kill anyone in Level 3: The Way to Rivendon
Don't kill anyone in Level 4: The Cliffside Fort
Don't kill anyone in Level 5: The Walls of Rivendon
Don't kill anyone in Level 6: Longwall Prison
Don't kill anyone in Level 7: Shortwall Barracks
Don't kill anyone in Level 8: The Roads of Lowerton
Don't kill anyone in Level 9: Lowerton Storage
Don't kill anyone in Level 10: Lowerton Worksite
Don't kill anyone in Level 11: Rivendon Harbour
Don't kill anyone in Level 12: The Streets of Rivendon
Don't kill anyone in Level 13: Rivendon Uptown
Don't kill anyone in Level 14: The Castle District
Don't kill anyone in in Level 15: Rivendon Castle
Complete Level 15: Inside the Castle
Earn all the Achievements in Shadwen
Complete the game sparing the King's life after Lily discovers you're a killer
Complete the game by leaving some or all of the guards alive, but killing the King
Complete the whole game killing all the guards and the King
Complete the whole game without letting Lily know you're a killer