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