Here is the full list of all 20 Sundered: Eldritch Edition achievements worth 1,000 gamerscore.
Unlock your first Ability
Survive your first horde
Defeat you first Miniboss
Corrupt your first Ability
Destroy your first Elder Shard
Destroy seven Elder Shards
Corrupt seven Abilities
Defeat all Minibosses
Unlock all Abilities
Find all Perks
Equip three Perks simultaneously
Defeat Dominion
Defeat Hysteria
Defeat Legion & Salvation
Defeat Nyarlathotep
Defeat Nyarlathotep & The Shining Trapezohedron
Defeat Humanity
Equip your first Perk
Collect 10,000 Shards
Collect 500,000 Shards