Here is the full list of all 11 Dear RED - there are Extended achievements. It takes around 0-1 hour to unlock all of the achievements on Windows.
You killed the murderer in front of his daughter
You found a secret conversation
You brought the end to that beautiful place.
You did what you didn't expect yourself to do.
You're a good person, Red
You ended your misery, and his.
There was something you don't know about the murderer
You left and let the murderer live with his daughter
You didn't allow your heart to be warmed again
You met the murderer's daughter
The murderer found out you were lying to him