Scene obtained by starting the fight with the lowest HP value e.g. Gladiolus, Prompto and Ignis being dead as combat ends from a fight previous to starting the Adamantoise Hunt.
I started by using the caravan at Hammerhead, fast travelled to Lestallum and picked up the hunt *Dead General Strikes Down the King* for the Zanmato (Death) on my NPCs. No need to finish the hunt (although how you kill your party is entirely your preference!)
Finally return to Hammerhead through rest fast travel, MAKE A MANUAL SAVE (so you do not have to repeat the above process again) and pick up the quest.
During the fight I used Freeze to trap all allies behind the Adamantoise front claws. Damage and slows actions making them easier targets. Wax and repeat, killing as many of them as you can until you get the summon scene.
I was using the Aranea glitch because of Titans summoning requirement, which is based upon the amount of dead and nearly dead allies (HP calculator for the entire party).
Hope it helps!
