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 everything in the game
Find all thump shards / spare thumps
Talk to Stanley five times
Party in the Rave Cave for 11 minutes and 12 seconds
Stun 5 enemies with a single Bananarang
Find all five baggies
Break the pot breaking record
Buy any trail mix
Kill an enemy after both Finn and Jake have attacked it
Store a Convict Fairy in a baggy
Complete the Door Repair quest
Complete sword training
Complete the Trading Game quest
Beat Starchy's Graveyard Fun Run
Find every Gunter cave
Complete the Dungeon Drama quest
Complete the Fear Temple
Receive every curse
Complete the Dream Temple
Kill a Lub Glub using Flambo
Complete the Terrible People quest
Lie to Marceline
Complete the Cinnamon Fun! quest
Complete the Love Note quest
Use Grabby Hand on a Pie Fairy
Find a thump shard
Chop down 999 bushes
Complete the Song Temple
Buy something from Choose Goose
Find a gum globe
Complete the tutorial