Here is the full list of all 31 ColdSide achievements.
Complete first level
Read all notes on the first level
What's going on with you?
You're at the place
Start playing ColdSide
Find all the figurines on the first level
Find all the figurines on the second level
Find all the figurines on the third level
Find all the figurines on the fourth level
Collect all figurines on the sixth level
Complete second level
Complete 3rd level
Finish Level 4
Complete Level 5
Finish Level 6
Get one of the alternate endings
Get True Ending
You don't remember anything
Find all figurines in level 5
Join the rebels
You've been torn to shreds.
Read all notes on the second level
Read all notes on the third level
Read all notes on the fourth level
Strange anomaly
Don't pet the cat
Finishing the game without dying
Open a closed door
Find the monster figurine
You took a dip in an anomalous pool
You have taken a card from a Foundation soldier without violence