Here is the full list of all 25 Scribblenauts Unlimited achievements. It takes around 8-10 hours to unlock all of the achievements on Windows.
Get all 106 Starites
Help all 40 of Maxwell’s brothers
Bring 60 Starites to Lily
Get all object Shards in the Misc category
Get all 217 object Shards
Get all object Shards in the Living category
Get all object Shards in the Food category
Get all object Shards in the Vehicle category
Bring 50 Starites to Lily
Get all object Shards in the Tech category
Get all object Shards in the Weapon category
Get all object Shards in the Music category
Bring 40 Starites to Lily
Download a custom object from another player
Create an object using the Object Suggestor
Bring 30 Starites to Lily
Change your Avatar
Get all object Shards in the Clothes category
Bring 24 Starites to Lily
Bring 16 Starites to Lily
Bring 12 Starites to Lily
Bring 8 Starites to Lily
Bring 3 Starites to Lily and unlock the world map
Get all the Starites in any level
Make a new object using the Object Editor