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