Here is the full list of all 20 Sundered achievements. It takes around 25-30 hours to unlock all of the achievements on Windows.
Defeat Nyarlathotep.
Defeat Nyarlathotep & The Shining Trapezohedron.
Destroy seven Elder Shards.
Destroy your first Elder Shard.
Defeat Humanity.
Corrupt seven Abilities.
Defeat Legion & Salvation.
Collect 500,000 Shards.
Find all Perks.
Defeat all Minibosses.
Equip three Perks simultaneously.
Unlock all Abilities.
Defeat Hysteria.
Defeat Dominion.
Corrupt your first Ability.
Collect 10,000 Shards.
Equip your first Perk.
Defeat your first Miniboss.
Survive your first horde.
Unlock your first Ability.