Here is the full list of all 50 I Was a Teenage Exocolonist achievements.
Reach the end of age 10
The Helios Lands in age 15
Sneak Out to explore
Win a Vertumnalia event
Start your second life
Reach 100 in all 4 skills of one type
Reach 100 Rebellion skill
Get the Life on Earth Ending
Get the Transcended Time Ending
Get the Ran Away Ending
Get the Joined the Gardeners Ending
Get the Disabled the Array Ending
Get the Tangent's Cure Ending
Get the Colony Destroyed Ending
Get all 29 Endings
Unlock Anemone on the Main Menu
Unlock Cal on the Main Menu
Unlock Tangent on the Main Menu
Unlock Dys on the Main Menu
Unlock Marz on the Main Menu
Unlock Tammy on the Main Menu
Unlock Rex on the Main Menu
Unlock Nomi-Nomi on the Main Menu
Unlock Vace on the Main Menu
Unlock Sym on the Main Menu
Unlock all characters on the Main Menu
Pet your Pet
Own four different pets at once
Saved Tammy
Saved Uncle Tonin
Saved Professor Hal
Ended the famine
Helped Tangent cure the Shimmer disease
Meet Sym the Gardener
Help Nomi confess their love to Rex
Break up Anemone and Vace
Prevent Cal and Tammy from dating
Get 5 relationships to 5 hearts
Score 75 in a single hand
Get a single card to value 50 or higher
Win 10 card games in a row in hard mode
Get a flush of five 5s
Win an Impossible challenge in hard mode
Have a deck of cards of a single color or wildcards
Unlock every card in the gallery (a lot more than 151)
An experimental treatment for your delusions
Kill a Faceless
Replace Governor Lum
Stop Tangent's engineered plague
Negotiate with the Gardeners at the end of age 19