This historic win happened in the show's 25th season, and the show's overall 1219th episode titled "The Finals IV: 'Partner'" with only his Pikachu left standing tall at the end. Ash's team at the end of the Pokémon World Coronation Series are: Pikachu, Dragonite, Gengar, Lucario, Sirfetch'd, and Dracovish.
From all of us here, congratulations!