Volcanion

Volcanion is an excellent bulky attacker that can dish out massive damage with a STAB combination only resisted by Water- and Dragon-types. Volcanion also possesses defensive utility thanks to its good defenses and unique typing. It fits well on semi-Trick Room teams, which let Volcanion reliably OHKO several dangerous Pokemon like Heatran and Genesect without needing to take a hit beforehand. Diancie can set Trick Room for Volcanion while also beating Kyurem-B. Rillaboom and Zeraora can use Fake Out to allow Volcanion to create Substitutes and easily beat Water-types. In return, Volcanion reliably beats Steel-types for Diancie and Fire-types for Rillaboom. Volcanion can struggle to find attacking opportunities with its awkward Speed tier forcing it to take a hit if it doesn't have speed control, and several Pokemon like Kyurem-B, Tapu Fini, Dragapult, and Urshifu-R can easily switch into Volcanion and threaten it out. It also faces stiff competition as a Water-type from the aforementioned Tapu Fini and Urshifu-R, as well as a Fire-type from Heatran and Incineroar.