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