Here is the full list of all 10 Five Nights at Freddy's achievements worth 1,000 gamerscore.
Completed the custom night on hardest difficulty.
Experienced a jumpscare, and then... who knows?
Survived the 6th night.
Kept Freddy from getting to cams 4A or 4B during night 5.
Survived the 5th night.
Kept Foxy from escaping during night 4.
Survived the 4th night.
Survived the 3rd night.
Survived the 2nd night.
Survived the 1st night.