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