I just encountered the hardest boss so far for myself on Chaos difficulty. During the middle/end of Chapter 3, the fight with. His fucking burst move or whatever the fuck it's called was SO DANGEROUS. If any of my characters were grouped together it was practically instant death. I was around LV33 on Chaos when I beat him too. I had Sopheria on constant passive, all heal strategy. Asbel, Richard, and Pascal all had moves that exploited his weakness rather quickly so dealing damage wasn't a problem. My main issue was that special eleth move he had. What I ended up doing was changing all of my characters to "Avoid enemy" or passive strat when his meter was maxed out. This way he could only catch ONE ally with his bullshit power attack. It was EXTREMELY manageable and as soon as I implemented this strategy I took him out FAST.Richard's Uncle
And how much SP did I get for this battle on Chaos. Wait for it...5600! What the fuuuuuuuuuuuck! So crazy! It's not even funny how worth it is to play on the higher difficulties in this game. I'd suggest those struggling with the harder modes just to learn the battle mechanics better because in the long run it's TOTALLY worth it.
That fight pissed me off so much because of the one shottedness of it. It doesn't even come down to skill at that point, it's just *bam*, guaranteed death to one of your party members. That is a big cop out in terms of "dealing with damage" or a tough attack to dodge IMO, but whatever.