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