Having conquered all three of Akala Island’s island trials, the time has come to face off against the island’s strongest trainer. Start to approach the entrance to the ruins itself and Lillie will finally catch up. She’ll also kindly will your Pokémon party. Soon afterwards, the kahuna herself will make her grand entrance.
Island Kahuna Olivia
Kahuna Olivia is a master of the Rock-type, so Water, Grass, Ground, Fighting and Steel-types will be your MVPs. There’s no shortage of Water-types between Brooklet Hill and the seas of Melemele of Akala. Meanwhile Grass-types are found in abundance in the Lush Jungle. For Ground and Steel, there’s Diglett.
Olivia’s first two Pokémon are both fossils. Anorith is part Bug, so it’s weak to Water, Rock and Steel-types. Obviously, don’t lead with a Grass-type since Anorith’s Bug Bite is super-effective. It will also steal you berry if your Pokémon has one.
Next us is Lileep, which is part Grass. This means Water and Ground-types need to switch out. Instead, fight it with Fighting or Steel-types. Ice-types are super-effective, but are of course weak to Rock and thus should be avoided if possible.
Olivia’s crown jewel is her Midnight Form Lycanroc, which looks extremely menacing. It knows Bite, which can flinch, and Rock Tomb to deal damage and lower Speed. Most important of all, it can use the Rock-type Z-Move. Fighting, Ground and Steel-types are ideal, to reduce the damage from its Z-Move.
Afterwards, you’ll be take outside the ruins. At this point, you can head straight to Hano Grand Resort to begin the process of leaving the island.
For reference, the resort is situated directly east from Heahea City, if you keep following the main road. Earlier, a Stoutland and its rider were blocking the way, but they’ll be long gone by now.