Kingdra

Water

Kingdra's access to Swift Swim and a strong STAB move in Hydro Pump makes it one of the best wallbreakers and sweepers under rain, heavily denting most Pokemon in combination with its STAB Draco Meteor. Although this STAB combination is resisted by many Pokemon, Kingdra's access to Ice Beam helps out in letting it hit threats like Tapu Bulu and Cradily. Kingdra has pretty decent bulk and a neutrality to Electric- and Grass-type attacks, which helps given the fact that it needs to continuously switch in throughout a match. While Kingdra can outspeed the entire unboosted metagame in rain, its Speed is underwhelming outside of it. Additionally, without rain boosting its Water-type STAB moves, Kingdra's Special Attack is unimpressive. Therefore, it requires specific team support that limits Kingdra to rain teams.