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