how to defeat vishnu-flynn

dont bother exploiting weakness just attack with your strongest attack

get demons with resist gun and null/light/dark, resist light and dark would do too drain/repel better
those demons must have no weakness against Zio or force attacks

resist gun only not null/repel/drain, the reason for this is for the whole party to share the gun attacks therefor lesser chance of a party member dying

AVOID making him smirk by  having your demons weakness exploited
if he smirks and land a almighty attack on you its the end

Skills needed

Fang breaker or other attack decreasing skills as long as you can maintain it
mediarahan - full heal
Imposing stance - should be used at the 1st 2 turns because vishnu-flynn can over power you at 1st


Optional skills
Energy drain - to help your demon maintain their skills

Recommended partner
Navarre - mainly because of support skills


Recommendation
use high level demons with high hp[900+ preferred]  with resist gun and null light/dark
make sure his attack is lowered by spam fang breaker or your preferred skill for lowering attack

Reminder
this guide is for War difficulty