Kingdra

Kingdra's incredible speed in the rain thanks to Swift Swim, unique typing, and access to the spread move Muddy Water make it a top choice for a rain team. It is an exceptional late-game sweeper when backed by the rain boost due to the STAB Water-type spread move combined with its quite decent Special Attack stat. Kingdra's unique typing also gives it many benefits; traditional Water-type checks such as Kyurem-B and Hydreigon are blown back by its secondary STAB move, and defensively, the typing only leaves it with two weaknesses while giving it handy resistances to common attacking types like Water and Fire. However, Kingdra has very mediocre stats across the board, including both defenses. It is wide open to being sniped by priority attacks such as Talonflame's Brave Bird and Bisharp's Sucker Punch after only a bit of prior damage. It also faces competition from other common Swift Swim users such as Ludicolo and Mega Swampert; the former can break past bulky Water-types, the bane of Kingdra, and the latter is immune to Thunder Wave, which cripples Kingdra for the entirety of the match. Finally, Kingdra is nearly worthless without its preferred field conditions intact. If it is not raining or the opponent has the speed advantage from using Trick Room or Tailwind, Kingdra is completely ineffective.