Here is the full list of all 17 Corpse Party achievements.
Viewed every ending.
Attained all endings and found every name tag.
Attained the "loop ending" to Chapter 5.
Attained the alternate ending to Chapter 5.
Attained the true ending to Chapter 5.
Completed Tooth.
Completed She Knows a Key.
Attained all endings in Chapter 4.
Completed Chapter 4.
Attained all endings in Chapter 3.
Completed Meeting of the Minds.
Completed Chapter 3.
Attained all endings in Chapter 2.
Completed Chapter 2.
Attained all endings in Chapter 1.
Completed A Gentleman's Errand.
Completed Chapter 1.