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 three levels in each Ambient Forever zone.
Complete three levels in each Force Forever zone.
Complete three levels in each Sentient Forever zone.
Complete five levels in any Forever zone.
Complete all Ambient zones.
Complete the game.
Collapse the system in level F2-3 by feeding the Attractor.
Complete all Force zones.
Complete all Sentient zones.
Unlock all zones.
Complete all tutorial zones.