Here is the full list of all 11 Osmos achievements. It takes around 6-8 hours to unlock all of the achievements on Windows.
Complete all tutorial zones.
Unlock all zones.
Complete all Force zones.
Complete five levels in any Forever zone.
Complete the game.
Complete three levels in each Sentient Forever zone.
Complete all Ambient zones.
Complete all Sentient zones.
Complete three levels in each Ambient Forever zone.
Complete three levels in each Force Forever zone.
Collapse the system in level F2-3 by feeding the Attractor.