Tough one, huh? If you just got wiped out by a blue dragon, don't worry—it's not just you. This is almost certainly the hardest fight you'll have encountered up until this point in the story. Personally, I’d say Sogne the Icebound is the second hardest boss fight in Metaphor: ReFantazio altogether.
There are stronger, tougher bosses to fight after Sogne, but you’ll be able to tackle those whenever you want. What makes this a particularly challenging fight is that once you reach Sogne, you’re locked in.