Kingdra

Kingdra's Swift Swim gives it an unmatched Speed tier in rain, notably outspeeding Dugtrio, Aerodactyl, and Jolteon. Its good bulk and defensive typing allow it to consistently set up Rain Dance. This makes it a good cleaner, especially against frailer offensive teams. Compared to offensive Starmie, it outspeeds more Pokemon when rain is active and has more bulk, which lets it offensively check physical sweepers like Dragon Dance Tyranitar, Salamence, and Aerodactyl. It also outspeeds many notable Pokemon that offensive Suicune does not like Zapdos and Gengar. Additionally, the threat of Kingdra can scare frailer offensive teams into sacrificing important special checks like Tyranitar, Metagross, and Snorlax to prevent it from sweeping, enabling specially offensive partners like Suicune, Zapdos, Jirachi, and Celebi.

Unfortunately, Kingdra cannot boost its power outside of Rain Dance and has poor coverage. As such, it struggles to deal with special walls and Pokemon that resist Water. Notably, it is completely walled by Blissey, specially defensive Jirachi and Celebi, and common bulky Water-types such as Milotic and Suicune. Explosion users such as Metagross, Gengar, and Forretress can also check it in a pinch if they are healthy. Finally, Kingdra's sweep can also be neutered by status and Tyranitar's Sand Stream. It also faces stiff competition from offensive Starmie and Suicune. The former naturally outspeeds most Pokemon, has better coverage, and has access to Rapid Spin. The latter has far more wallbreaking power thanks to Calm Mind. Kingdra isn't seen often due to the above reasons, but it is a formidable threat if given the right support.