If you're reached this point, you'll have bested Alola's Elite Four, the strongest trainers there are. Go up the stairs to find the Champion's seat at the far end. It's all yours! As you begin to warm up the seat, Kukui will head over to congratulate you... and give you one final battle!
Pokemon Professor Kukui
|Incineroar (if Rowlet was chosen)||58||Fire/Dark|
|Primarina (if Litten was chosen)||58||Water/Fairy|
|Decidueye (if Popplio was chosen)||58||Grass/Ghost|
First up is Lycanroc. This mutt has high Attack and Stone Edge to really cause a dent. It can also use Stealth Rock to damage Pokemon that switch in and Accelerock to snipe weakened Pokemon with increased priority. Bulky Pokemon, especially Steel-types are great here.
Braviary is another heavy hitter with Brave Bird and Crush Claws. When it's not dealing damage, it's using Tailwind to improve its teammates' Speed or Whirlwind to switch your Pokemon, causing them to get hit by Stealth Rock if it's up. Face it with Rock or Steel-types if possible.
Magnezone is a monster with high Special Attack and good defences. It's doubly weak to Ground-types and weak to Fire and Fighting-types. On top of dealing lots of damage with its STAB moves, it has Thunder Wave to impair and Mirror Coat to punish special attackers.
Snorlax is a beefy obstacle with high HP, Attack and Special Defence, but dire Speed. Besides its signature Body Slam, it has strong Dark, Ground and Steel-type moves. Fortunately it doesn't have Rest, so you should be able to outlast the food-loving fiend.
Alolan Ninetales is massively weak to Steel-types and typically weak to Fire, Rock and Poison-types. If you've got no Steel-types, Fire-types are good since they resist both of its STAB moves. Watch out for Ice Shard if your Pokemon is low on HP.
Finally, Kukui took the starter Pokemon that's strong against yours while nobody was looking. To make matters worse, it has the Z-Crystal that matches its primary Type. For a chance of survival, you need a Pokemon that's super-effective and also resists the primary Type.
Even still, you need to be mindful of the starter's secondary Type. Of note, Incineroar also has Fighting and Dragon-type moves, Primarina has Aqua Jet (which is mostly useless except to surprise you at low HP) and Decidueye knows the Flying-type Brave Bird.
This is where the going gets tough. Don't hesitate to use your own Z-Moves to finish off his starter Pokemon--you may as well fight fire with fire. Furthermore, we hope you've been saving those Max Revives, because you may need them!
Triumph against this final battle and...
You're now the Pokemon League Champion! Hopefully you've got some popcorn or snacks lying around (and a handkerchief), because the ending sequence is shortly about to begin.
Wait, there's just one more thing...
Tapu Koko has good Special Attack and impressive Speed; factored in the boost from Electric Terrain and you've got a difficult battle on your hands. To make things even trickier, its signature move Nature's Madness can halve your Pokemon's current HP like Super Fang.
Now, you are allowed to catch Tapu Koko at this point in time, but we don't really recommend it. Instead, make it faint and move on. It may be strong, but it's only a single Pokemon, so that should be an easy enough task. Use Ground or Poison-type moves if available.
Defeat or capture Tapu Koko and you'll receive the Tap unium Z , which transforms the Tapu Pokemons' signature move Nature's Madness into an exclusive Z-Move.
Return of the Tapu
After making Tapu Koko faint, you can come back to the Ruins of Conflict in your own time and the Legendary Pokemon will still be there. In fact, if you accidentally defeat it again, you can continuously make it reappear by defeating the Pokemon League.