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