Here is the full list of all 25 The Hidden and Unknown achievements.
You have read it all.
Feeling without Thinking is dangerous.
You have read all the main storylines in the game.
Thinking without Feeling is pointless.
Hate.
Feel second.
Love.
Depression.
Feel.
Think first.
Efficiency.
The Blitzkrieg.
The Black Swan.
Think.
You got far.
This is the end, or is it?
You have read the credits.
You are close.
The Real Challenge, or is it?
From The Bottom To The Top.
The Rock Bottom.
The Bottom.
The "Good" Old Times.
The future is not so bright, if you don't fight.
Sometimes, choice is only an illusion.