"However, unexpectedly, it turned out that it had dealt 360 damage points. At the same time, Frandy had been in a Frozen state for nearly two seconds.
I think it should be fatal strike as its said just a couple paragraphs up that landing a "Lucky Strike" would be impossible.
What the ****? Ok he can't do anything because he's slowed and trapped and he has the same build as you with high magic resist and garbage physical defence. Given that you have an Archer who has ranged physical attacks. You can ask her to stand at the edge of his range and hit him repeatedly and then Use the same counters and buffs you were using on yourself to Protect her. You use half the MP and potions and don't make her feel completely useless trying to solo a boss well in a party.