Lmfao I remember I did this once just for the fun of it. It was an easy win against the Elite Four. I also tried using my common starters I met and captured in my early game that I have trained to be high level and strong Pokemons against the Elite Four. That one was a lot better in terms of combat since there's a challenge. If you use Rayquaza against the Elite Four, you can easily dismantle them.