Here is the full list of all 30 Tiny Tina's Assault on Dragon Keep: A Wonderlands One-shot Adventure achievements.
Fed thy noble queen 3 times during one visit to her quarters
Completed thy quest by rescuing yonder queen
Remained in Zero's Deception mode for ten seconds straight
Completed the mission "Shoot This Guy in the Face"
Showed thine worst enemy, the abomination known as "The Darkness", who is the nerdiest of them all
Unlocked 10 customization items
Used the Lootapult to cause a Lootsplosion
Redeemed 25 tokens
Purchased 5 items from the black market
Reached level 10
Unsheathed 5 swords from Immortal Skeletaurs without leaving the area
Introduced thyself to the White Knight
Demonstrated your skill, or lack thereof, at rolling the magical treasure orb of many sides
Revived someone from "Fight for Your Life!" that is on your friends list
Reached level 5
Slew Mister Boney Pants Guy
Completed level 1 of all challenges with a single character
Reached level 25
Reached level 35
Had Purple-rated gear or better equipped in every slot
Killed 100 enemies with the Sabre turret
Phaselocked 100 enemies
Gunzerked continuously for 90 seconds
Killed a Chubby
Completed all side missions
Won the most challenging round in Murderlin's Temple
Wielded the Mysterious Amulet
Vanquished the Ancient Dragons of Destruction
Killed 100 enemies with Deathtrap
Killed 100 enemies while using Buzzaxe Rampage