Ash demonstrated all his experience, And iris was the victim this time
I think we all saw that in terms of "power" Angrynite was destroying Happynite, we all saw that Iris's Big Mistake was approaching that Dracovish Mouth. I mean, even if a Mega Mewtwo gets close to the claws of a Crawdaunt with Guillotine, no matter how extremely powerful he is, Mewtwo will lose.
Iris understood this, and attacked Dracovish from afar, and as expected, Mr Fish was defeated in an instant. What happened after? Haxorus was dominating a Happynite that had been destroyed by Angrynite, But then, something happened, that uncontrollable factor, that creative thinking of Ash.
Happynite use everything to him advantage, the weather, Hurricane, Dragon Pulse ... and magic happened, Dragonite learned new attack, the devastating Draco Meteor, Iris couldn't dodge because this attack took her by surprise.
Iris's mistakes?
-Only depend on physical strength
-Not having the Movement "Protection' for these types of situations
In conclusion, she lacked experience, That same experience that Ash has after hundreds of battles, that's why, even if a trainer has a Legendary Pokemon, if he bumps into someone who is close to being a POKEMON Master, ...Will pay dearly
it does not matter if the latter uses a Caterpie, the experience is not bought.
Power levels were respected until the end in this battle.