Here is the full list of all 24 Kindergarten 2 achievements. It takes around 8-10 hours to unlock all of the achievements on Windows.
Remembered that Nugget likes flowers.
Saw something gross.
I'm so proud of you.
Collect all of the outfits.
Everything.
Help Ted foil his brother's plan.
Collect all 50 Monstermon Cards.
Found homes for all of Agnes's cats.
Win all the Monstermon battles.
Help Lily and Billy save the captured kids.
Help Ms. Applegate get her fix.
Help Carla get the device that Jerome has.
Help Felix get his full inheritance.
Help Nugget dig a new Nugget Cave.
Help Buggs get his knife back from Penny.
Win a Monstermon battle.
Collect the specimens for the science teacher and use them appropriately.
Collect 10 Monstermon Cards and make a full deck.
Help the Janitor win the war against Bob.
Change your outfit.
Get through your first day of school.
Help Ted prove his worth to Felix.
Collect your first Monstermon Card.
Die for the first time.