Skylight Freerange 2: Gachduine (Damage is just a number)
Here are the steps I took to get a billion damage points in one shot:
Main Character:
Specialist Character Class: 50% fire initially and 200% fire at level 100
Full Rocket Launcher Competency
Full Offense Competency
Full Elemental Competency
(I didn't have full stealth competency but this could help)
Biomachine Equipped (+50 Attack)
Rocket Launcher with fully upgraded attack in both slots (+40 attack)
Miranda (Healer):
Biomachine Equipped for Fog of War (3x attack in Symbiote Cloud)
Target a fire weak symbiote with main character and Rocket Launcher and put down a symbiote cloud with Miranda. Get as close as you can (Danger Zone competency makes close Rocket Launcher attacks stronger) and fire. In the video my party died but the trophy still unlocked.