Here is the full list of all 30 The Dark Pictures Anthology: Little Hope achievements worth 1,000 gamerscore.
Completed the Solo Story
Saved Mary
Saved Andrew
Saved John
Completed 5 combat events in succession
Found all of the black framed Pictures
Defeated Taylor's demons
Saved Taylor
Rational was one of top two traits for John
Headstrong was one of top two traits for Taylor
Maximized Daniel and Taylor's Relationship
Completed the prologue
Find all witchcraft secrets
Finish Movie Night
Unlock Daniel's Amiable Trait
Unlock Andrew's Compassionate Trait
Unlock Angela's Understanding Trait
Choose all of the Heart decisions
Choose all of the Head decisions
Daniel must survive
Angela must survive
Find all of the white Framed Pictures
Everyone must die at the ruined house
Everyone must survive
Maximize Angela and John's relationship
Andrew must have a good relationship with all characters
Find all family secrets
Find all of the Pictures
Kill all Characters
Andrew must be the sole survivor with a weapon