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