Here is the full list of all 46 Adventure Time: Explore the Dungeon Because I DON'T KNOW! achievements.
Complete all of Starchy's Quests.
Collect every Sub-Weapon.
Find all of BMO's Game Cartridges.
Complete all of Princess Bubblegum's Quests.
Survive a Monster Floor
Uncover Bubblegum's dark secret.
Complete all of Susan Strong's Quests.
Overcome the Guardians' punishment.
Fully upgrade Ice King.
Free Flame Princess.
Complete all of Mr. Pig's Quests.
Eat every Food item at least once.
Enter the Nightosphere.
Fully upgrade Marceline.
Free the Earl of Lemongrab.
Complete all of Tree Trunks' Quests.
Weather Goliad and Stormo's psychic assault.
Locate every Familiar.
Rescue the Hyoomans.
Upgrade a Sub-Weapon into a stronger one.
Assist Gunter with a feisty feline.
Upgrade a character's Imagination.
Put Ice King in his place.
Grab 50 Treasures on a single Treasure Floor.
Buy something from the shop.
Receive a Curse.
Upgrade a character's Focus.
Outrun the stampeding prisoners.
Upgrade a character's Rowdiness.
Outsmart the Demon Cat.
Perform a Perfect Block.
Pick up every Item pickup at least once.
Upgrade a character's Thumps.
Return from the Dungeon alive.
Complete a Quest for the Princess.
Use a Special Attack.
Fully upgrade Finn.
Fully upgrade Jake.
Fully upgrade Cinnamon Bun.
Fully upgrade LSP.
Fully upgrade Lemongrab.
Fully upgrade Flame Princess.
Survive 15 Floors in one Nightosphere run.
Survive 25 Floors in one Nightosphere run.
Survive 50 Floors in one Nightosphere run.
Collect every Token.