Marianette, Angie and Ryland
None of the mons in my team were fully evolved when I confronted Marianette so getting through her team was pretty difficult, especially her bulky Bewear
I swept through Angie's team quite easily in V10 but the double battle it is now was hell and I had nothing to remove her field so I had to spam healing items on my Medicham with my second pokemon while he swept with high jump kick (I've lost count of how many times I lost because it missed lol, never trust a 90% accuracy)
Had to use all the remaining revives I had to beat Ryland, and I really had an hard time beating his Claydol and Torterra because of how bulky they were (also it took me a while to understand why my Talonflame was powerless against Torterra xd)