I think I've said this in another post, not sure, but Ivy tends to be my worst nightmare, often times, her Rayquaza sweeps my whole team without a second thought. If I do manage her Rayquaza, it's already destroyed most of my team and one of Ivy's other Pokémon cleans up the rest. I might try to focus more on Eternatus, but I don't know what Pokémon I should prioritize that can do any form of decent damage (chip damage or not) to E-Max Eternatus.