"He knows he is," Shiranui interjected, "I'm Shiranui Tsukiko, Sea Hero of the Whirl Islands and Champion of the Kanto and Kalos Leagues."  He sent out his most powerful partner: Saisei the Mewtwo.
"[i]If you truly wish to take on the most powerful Pokémon, I'm right here,[/i]" stated Saisei.