You can get this Achievement on 2nd or 3rd Playthrough on any Difficulty
Weapons : Credits required to fully upgrade
Stun Baton : 11,700
BI-55 Pistol “Hand Cannon” : 2,800
GRP Glove (Gravity Restraint Projector) : 11,700
TK4 Riot "Shotgun": : 4,200
Skunkworks Shotgun : 6400
UJC Special OPS “Tactical Pistol” : 5700
UJC Special Ops "Assault Rifle": : 11,000
Total Credits required to fully upgrade All Weapons : 53,500
Even though this is listed in the Hardcore Mode, you can simply get this by doing NG+. You will need 54,500 Callisto Credits in total to upgrade everything. Depending on how well you did on the initial run, you could get this by your second turn through the game. Here's a breakdown on the cost of every weapon:
"Stun" Baton:
Tier One
Riot Control Swing – 300 Callisto Credits
Blocking Counter Attack – 300 Callisto Credits
Increased Velocity Allow Sheath – 300 Callisto Credits
Tier Two
Damage Upgrade Level One – 900 Callisto Credits
Blocking Protection – 900 Callisto Credits
Block Break – 900 Callisto Credits
Tier Three
Damage Upgrade Level Two – 2,700 Callisto Credits
Blocking Feedback Damage – 2,700 Callisto Credits
Targeting Module Upgrade – 2,700 Callisto Credits
BI-55 Pistol “Hand Cannon”:
Tier One
Stability Upgrade – 200 Callisto Credits
High Capacity Magazine Upgrade – 200 Callisto Credits
Tier Two
Magnum Rounds Damage Upgrade – 600 Callisto Credits
Tier Three
TK23 “Boom Bullets” – 1,800 Callisto Credits
"GRP" Glove:
Tier One
GRP Recharge Speed Upgrade Small – 300 Callisto Credits
Energy Upgrade Small – 300 Callisto Credits
GRP Velocity Upgrade Small – 300 Callisto Credits
Tier Two
GRP Recharge Speed Upgrade Medium – 900 Callisto Credits
Energy Upgrade Medium – 900 Callisto Credits
GRP Velocity Upgrade Medium – 900 Callisto Credits
Tier Three
GRP Recharge Speed Upgrade Max – 2,700 Callisto Credits
Energy Upgrade Max – 2,700 Callisto Credits
GRP Velocity Upgrade Max – 2,700 Callisto Credits
TK4 Riot "Shotgun":
Tier One
Magnum Rounds Damage – 300 Callisto Credits
Stability Upgrade – 300 Callisto Credits
Tier Two
High Capacity Magazine Upgrade – 900 Callisto Credits
Tier Three
Explosive Round Upgrade – 2,700 Callisto Credits
Skunkworks "Shotgun":
Tier One
Magnum Rounds Damage – 300 Callisto Credits
Tier Two
Stability Upgrade – 1,200 Callisto Credits
Magnum Rounds Damage Upgrade – 1,200 Callisto Credits
Tier Three
Swarming Rounds Upgrade – 2,700 Callisto Credits
UJC Special OPS “Tactical Pistol”:
Tier One
Magnum Rounds Damage Upgrade – 300 Callisto Credits
Tier Two
High Capacity Magazine Upgrade – 900 Callisto Credits
Stability Upgrade – 900 Callisto Credits
Tier Three
TK33 “Burst Mode” – 3,600 Callisto Credits
UJC Special Ops "Assault Rifle":
Tier One
High Capacity Magazine Upgrade – 500 Callisto Credits
Tier Two
Magnum Rounds Damage Upgrade – 1,500 Callisto Credits
Tier Three
Stability Upgrade – 4,500 Callisto Credits
TK63 “Homing Rounds” – 4,500 Callisto Credits
Credit: otaku1412