Here is the full list of all 20 Chasm achievements worth 1,000 gamerscore. It takes around 15-20 hours to unlock all of the achievements on Xbox One.
Defeat a boss without getting hit.
Unlock all the Bestiary entries.
Defeat Ulak.
Find all the Journal Entries in the game.
Explore 100% of the map.
Break all the crates in the game.
Defeat the Shaman.
Find all the Powerups in the game.
Defeat King Trell.
Rescue all the missing villagers.
Become the Arena champion.
Spend 5,000 gold.
Defeat the Titan.
Defeat 1,000 enemies.
Defeat the Bone Worm.
Defeat the Wendigo.
Defeat 100 enemies.
Complete the game on Hard difficulty.
Complete the game as a Mortal.
Complete all villager sidequests.