Here is the full list of all 25 Idle Galaxy achievements.
Purchase 20 perks
Complete 10 levels
Purchase 200 upgrades
Create 10000 particles
Purchase 100 upgrades
Purchase 50 upgrades
Create 1000 particles
Complete 5 levels
Purchase 20 upgrades
Create 100 particles
Complete 1 level
Create 10 particles
Purchase 50 perks
Purchase 100 perks
Purchase 200 perks
Create 1 galaxy
Create 5 galaxies
Create 10 galaxies
Complete 20 levels
Complete 50 levels
Complete 100 levels
Complete the game
Play 10 hours
Create 100000 particles
Create 1000000 particles