Full list of all 54 Enter the Gungeon achievements. It takes around 120-150 hours to unlock all of the achievements in the base game on Windows.
The base game contains 48 achievements, and there are 2 DLC packs containing 6 achievements.
Complete Frifle's Challenges
Steal 10 things
Kill 100 enemies by dropping chandeliers
Kill 100 enemies while riding in a mine cart
You've met with a terrible fate, haven't you
Complete the game with Beast Mode on
Map the first Five Chambers for the lost adventurer
Populate the Breach
Ace Winchester's game 3 times
Always be flipping. Guns are for flippers
Die in the Past
Unlock the Robot
Clear the Sixth Chamber
Unlock the Bullet
Complete the game with the Sorceress's Enchanted Gun
Complete all 4 main character Pasts
Kill the Pilot's Past
Collect five Master Rounds in one run
Clear the Fourth Chamber 20 Times
Clear the Second Chamber 40 Times
Clear the Fifth Chamber 10 Times
Kill the Convict's Past
Open the shortcut to the Fifth Chamber
Clear the Third Chamber 30 Times
Deliver the Golem's replacement arm
Kill the Hunter's Past
Kill the Marine's Past
Construct the Bullet that can kill the Past
Kill a Jammed Boss
Accessed the Hidden Market
Clear the First Chamber 50 Times
Fall at the last second
Carry a large amount of money at once
Open the shortcut to the Fourth Chamber
Kill 100 enemies by knocking them into pits
Kill a boss after covering it with glitter
Kill a frozen enemy by rolling into it
Win a wager against the Gunsling King 5 times
Defeat the Boss of the Fifth Chamber
Spend big at the Acquisitions Department
Open the shortcut to the Third Chamber
Access the Temple
Avenge Manuel
Open the shortcut to the Second Chamber
Why
Get the jump on a Mimic
Access the Oubliette
Complete the Tutorial
Complete Daisuke's trial
Kill the Robot's Past
Kill the Bullet's Past
Defeat an Advanced Boss
Complete Tonic's Challenge
Take Revenge