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
Defeat Spider Queen boss
Defeat Leviathan boss
Defeat Treant boss
Complete the Prologue and all their secondary quests
Get 1k of crystals in single player
Kill 10 enemies
Use the teleporter to travel between zones
Kill 10 enemies while they are frozen
Disarm 10 traps with the Hunter in single-player mode
Die 10 times in single-player mode