Here is the full list of all 47 DROD: The Second Sky achievements.
Kill a man-eating dungeon roach
Complete the challenge in TH:2S1W
Complete the challenge in TH:1N5W
Complete the challenge in TO
Complete the challenge in GG
Complete the challenge in SWaRBS
Complete Chapter 1
Complete the challenge in IU:1N
Complete the challenge in HitF
Receive an answer from the Truth Vessels
Clear the secret area in SutO
Complete Chapter 2
Complete Chapter 3
Complete the challenge in SM:1E
Complete the challenge in SM:4E
Complete Chapter 4
Complete the challenge in EotS
Complete the challenge in EoA:3S
Complete the challenge in EoA:2E
Complete Chapter 5
Complete the challenge in WBCEND:1E
Complete the challenge in WBCEND:1N1E
Complete Chapter 6
Complete Chapter 7
Complete the challenge in S.Ga.
Step kindly all the way through TLW
Complete Chapter 8
Complete Chapter 9
Be kind in HitF
Be mean in HitF
Complete the quest for the plate
Looking for hard questions
The end of the journey
Complete the final chapter
Completed all of Arky's challenge rooms
Touch the secret checkpoint in FW
Complete the challenge in TRA
Complete the challenge in MOAR
Complete the challenge in CW
Saw the second sky
Completed FB level
Completed R level
Completed D level
Completed BM level
Completed Bomberman challenge
Completed Roachu Rocket challenge
Completed The Second Sky and cleared all secret rooms