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