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