Here is the full list of all 29 Ad Infinitum achievements worth 1,000 gamerscore.
Grant hope to despair.
Grant clarity to corruption.
Grant healing to pain.
Kill despair.
Kill corruption.
Kill pain.
An act of compassion.
An act of courage.
An act of mercy.
Walk the path of Despair.
Walk the path Corruption.
Walk the path of Pain.
Look at your Reflections.
Find all french identification bracelets.
Find all german identification plates.
You have passed through the fire and been reborn.
Reunite with your family.
End up in the Asylum.
Finish the Prologue.
Fully assemble the mirror.
Have a seance.
Survive the first encounter with Rage.
Survive the first encounter with Hunger.
Survive the first encounter with Mayhem.
Get killed by a creature.
Light all six searchlights.
Inspect all paintings in the house.
Answer the field-telephone six times.
Read all letters.