Trails SC end spoilers
I'm sure his damage is probably the main buff he got since he does 3k normal attacks with his s-breaks doing 8-9k depending on your adf. Maybe he also didn't have the two minions either, or maybe his clones got an HP buff? I'm not sure on the details besides the clear damage buff. But yeah, the fight was really satisfying after barely pulling out the win. Kevin's s-break saved my ass too many times to count.
If you can believe it
I actually beat that fight without Kevin. My party was Estelle, Josh, Kloe and Olivier. I was running with my best characters and I refused to change even though I knew Kevin would be a godsend. It was rough.