Here is the full list of all 35 Adventure Time: The Secret Of The Nameless Kingdom achievements.
Choose Slumber Princess to rule
Beat the game with 3 thumps, without upgraded sword, shield, or armor
Choose Lullaby Princess to rule
Choose Nightmare Princess to rule
Find all thump shards / spare thumps
Find everything in the game
Stun 5 enemies with a single Bananarang
Receive every curse
Complete sword training
Find all five baggies
Complete the Door Repair quest
Talk to Stanley five times
Find every Gunter cave
Complete the Trading Game quest
Lie to Marceline
Break the pot breaking record
Chop down 999 bushes
Party in the Rave Cave for 11 minutes and 12 seconds
Beat Starchy's Graveyard Fun Run
Complete the Dungeon Drama quest
Store a Convict Fairy in a baggy
Complete the Fear Temple
Kill an enemy after both Finn and Jake have attacked it
Use Grabby Hand on a Pie Fairy
Complete the Dream Temple
Find a thump shard
Kill a Lub Glub using Flambo
Complete the Love Note quest
Complete the Terrible People quest
Complete the Cinnamon Fun! quest
Buy any trail mix
Complete the Song Temple
Buy something from Choose Goose
Find a gum globe
Complete the tutorial