Oh man, Air Buster wrecked my ***.
After seeing a few videos on Shinra Company + and noting that my potential setup was not as nearly as good as the ones on YouTube, I thought I'd get wrecked too. I've never even attempted a bonus battle before, which didn't help.
I tried it anyway with my ragtag group and absolutely destroyed all 4 bosses. Stop magic made Air Buster a joke since it halted all counterattacks, and Aeris' default SB (Seal Evil) silenced all of the adds on the 3rd boss. I ended up using Stop on that boss too and hardly took any damage at all. For the 4th fight, I used Blade Beam as my RW skill twice, which almost took out the dog right off the bat. I finished the dog off with normal skills, used Stop on Rufus, and it was over pretty quickly after that.
TLDR: Stop magic is seriously underrated in the Shinra Company + fights.