Suicune

Suicune is one of the best Water-types in the format thanks to its great all-around bulk. With its good physical and special defenses, it can be very difficult to take out for some teams, and with Pressure, it can be very effective at stalling other Pokemon out. It's able to check a lot of Pokemon in the metagame such as Garchomp, Mega Kangaskhan, Blaziken, Mega Salamence, and Mamoswine. It often runs Calm Mind to become more threatening offensively as well and has solid Water- and Ice-type coverage that covers most of the metagame bar other Water-types. Suicune can run a variety of viable sets, including moves that can throw off your opponent's game plan such as Mirror Coat, Icy Wind, and Substitute. It has a decent Speed tier for a defensive Pokemon, outspeeding foes such as Porygon2, Tyranitar, and, with some investment, also others such as Rotom-W and Cresselia. However, Suicune's low Special Attack means it needs a few Calm Mind boosts before it can do significant damage. Its only recovery is Rest, which can be somewhat unreliable. If it takes too many hits early on in a match and is forced to use Rest, it is often not as good at dealing with strong threats late-game such as Mega Salamence, Blaziken, and Mega Kangaskhan.