Here is the full list of all 25 Tower of Waifus 2 achievements.
Finish the game with Mysterious Knight character
Dead by attacking the Demon Lord
Choose wrong 8 answers in the battle
Kill 20 enemies
Kill 5 enemies by Knight
Dead by a trap
Watch the opening
Watch the secret ending
Finish the Epilogue
Finish the game with Young Arrogant Hero character
Defeat and talk to the boss
Enter the 9th floor
Win the 8th floor
Choose correct 8 answers in the battle
Dead by a magic beam
Win the 7th floor
Win the 6th floor
Win the 5th floor
Win the 4th floor
Kill 5 enemies by Sword Man
Win the 3rd floor
Win the 2nd floor
Win the first floor
Kill 1 enemy
Fail the 1st floor