Here is the full list of all 14 Critter Crunch achievements.
Complete Challenge mode
Complete both Adventure mode and Puzzle mode
Survive to level 9 in Survival mode
Complete 35 Adventure levels while also feeding Smalls to completion
Unlock Survival mode
Complete 6 Combos in a single level
Reach experience level 5 in online Versus mode
Win an online Versus match
Complete 10 Food Chains in a single level
Complete 25 Puzzle levels
Unlock Challenge mode
Complete a puzzle level with moves remaining
Unlock Puzzle mode
Pop a chain that is 15 critters long