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