According to the search results, Suicune is a legendary Water-type Pokémon that is vulnerable to Electric and Grass-type moves. Therefore, the best counters against Suicune are strong Electric and Grass-type Pokémon such as Zapdos, Raikou, Electivire, Roserade, Tangrowth, and Alolan Exeggutor. It is recommended to start the battle against Suicune with the strongest Electric-type Pokémon before moving onto Grass-types if needed.