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