Here is the full list of all 12 Heaven Will Be Mine achievements.
Beat the game as Saturn
Beat the game as Luna-Terra
Beat the game as Pluto
Beat the game as all three characters
Beat the game with the CM ending
Beat the game with the MF ending
Beat the game with the CG ending
Get all three endings
Make a choice for the first time
See all chats
Get An Easter Egg
Play As Luna-Terra and get an ending other than MF