Challenge playlist:
• Digimon Story Cyber Sleuth: Hacker's Memor...
The first of the game's postgame bosses. Venom Myotismon is worse than satan himself apparently, and his number is the number of the beast, around which his entire moveset is based. The boss can proc poison with his special and instadeath with Destruction, and he's got a number of darkness-elemental tools in his arsenal, which are about as damaging as you would expect.
And therein lies the way to defeating the accursed villain. With all his sources of damage, Destruction included, being dark-elemental, equipping 3x Dark Guard DX on a party of three Digimon designated for the matchup reduces the damage to a mere 10% of what it would be otherwise. It's just impossible to bear if we don't resort to these defensive measures.
The best party to do this is a trio of Gryphonmons after inflicting Bug with SkullSatamon (a fitting Digimon to attack the boss), as they have triple accessory slots, unlike 2-accessory Vaccines, which are still taking 40% of the damage, which is still a tad too significant.
It's still a long battle but eventually the boss will perish.