Here is the full list of all 24 Sweet Dream Succubus - there are Nightmare Edition achievements.
Get all 3 endings.
Get a girlfriend
Solve her identity, her kind and her goal.
Beat the game in 3 loops
Get killed by the succubus.
Get looped by a movie.
Get the succubus master ending.
Get to credits screen.
Discover her full name
Get all events
Getting the church event
Making the shady guy talk.
Getting the hotel event
Discover her second name
Wear a condom!
Get the clinic event.
Getting the Jog event.
Skip a shower.
Starting a game loop.
Getting the movie event.
Getting the library event.
Discover her first name.
Getting the delivery event.
Starting a new game for the first time.