Here is the full list of all 11 Korgan achievements worth 1,000 gamerscore. It takes around 1-2 hours to unlock all of the achievements on Xbox One.
Complete the Prologue
Complete the Prologue and all their secondary quests
Defeat Treant boss
Die 10 times in single-player mode
Defeat Leviathan boss
Disarm 10 traps with the Hunter in single-player mode
Use the teleporter to travel between zones
Defeat Spider Queen boss
Get 1k of crystals in single player
Kill 10 enemies while they are frozen
Kill 10 enemies