an outbreak of Gigantimaxed Pokémon have been coming out around Galar without a known source, and your Pokémon just so happens to get affected by it.

Your strongest Pokémon was your Grimmsnarl, and it was now rampant and becoming increasingly violent by the minute, and trying to subdue it would have no effect. There wasn't much to do, since Gigantimaxed Pokémon are over a hundred feet tall, and are stronger than ever, so all you can do is try and calm it down to the best of your ability, but trying might be too dangerous.