I really can't tell because I zoomed through before and only won by losing twice and then buying as many revives and hyper potions as I could and now my team is too strong to test it out
but I'l use my best guess
aaron: bad choice, besides drapion
bertha: not a problem, it was definitely harder than aaron
flint: good, you're improving
lucian: easyish with my team, hard with some other teams
cynthia: I don't care what you say, she's good, although I usually only use roar of time and blast burn when I fight her, it's fun, burn/be destroyed by a time vortex baby burn/be destroyed by a time vortex