Here is the full list of all 48 Necromunda: Hired Gun achievements.
Fill one faction bar
Kill an enemy with every weapon
Finish the Main Campaign
Take out 50 shields with the grapnel
Finish Chapter 12
Finish Chapter 11
Kill 60 enemies with the Perfect Aim module
Place the 5 bombs in a gap of less than 3 minutes in Escher Lab
Finish Chapter 10
Kill Brickjaw in Koloss 44
Finish Kaerus without using any other weapons than the Ironfist
Kill 30 enemies with your Mastiff
Finish Avarus without using the grapnel
Finish a mission using only special weapons
Finish Chapter 9
Trigger all mines on Steel way
Complete the shooting training in Martyr's End
Finish Chapter 8
Find a +3 weapon
Finish Chapter 7
Kill 30 enemies with the Crush module
Finish a mission with an S rank
Kill 10 enemies in a row with headshots only
Finish Chapter 6
Open 20 chests
Upgrade one implant to the class 4
Finish Chapter 5
Finish Chapter 4
Kill 30 enemies with the Blast module
Kill 100 enemies by using Augmetics powers
Amass 100.000 credits
Buy an upgrade for your Mastiff
Customize every aspect of a single weapon
Finish Chapter 3
Kill 5 enemies in one use of Strength Booster
You have killed 100 enemies with a headshot
Finish your first secondary mission
Finish Chapter 2
Let Brickjaw live in Koloss 44
Pet your dog in Martyr's end
Buy your first upgrade to the Rogue Doc
Finish Chapter 1
You have performed 100 Takedowns
Wallrun 2500m
Kill 100 enemies while wallrunning
Finish all main missions with a rank of A or more
Kill a Genestealer with a grenade launcher
Travel 5km using the grapnel