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