Here is the full list of all 21 Snowflake's Chance achievements.
Reach the underground forest.
Reach the Elephant Bridge without dying.
Have attack, jump and health upgraded at the same time.
Befriend three Ghost Butterflies at once.
Have 3 different critters at the same time.
Discover a secret alcove.
Find a whacking stick.
Make it past the first tier.
Be a jerk to your scampering comrade.
You should have seen that one coming...
Survive the void.
Escape the lord of the Pit.
Walk the earth again.
End the nightmare.
End the nightmare with 25 Baubles.
Be nice.
End the nightmare without dying.
Sit on the Pit Lord's throne.
Earn back 3 chances.
Fly too high.
End the nightmare on Brutal Mode.