Volcanion

Volcanion is one of the most reliable Fire-types in Doubles OU thanks to its great defensive Fire / Water typing, good bulk, and high Special Attack stat. In stark contrast to most Fire-types, Volcanion is able to wall most opposing Water-types thanks to its Water Absorb ability, although it still struggles to do meaningful damage back to them. Volcanion sits at a middling Speed tier, so it's usually forced to absorb attacks before dealing its own in return. Its good bulk allows it to do this reasonably well, but it thrives best when it's supported by speed control like Tailwind or Trick Room. Offensively, Volcanion's typing offers decent STAB coverage but still leaves it walled by certain foes, including Water-types like Tapu Fini and Dragon-types like Mega Salamence. Volcanion can carry coverage moves to address some of its checks, but it suffers from four-moveslot syndrome in that it doesn't have enough room to pack all of the coverage moves it wants to run. Despite all of this, however, Volcanion can easily become a staple Pokemon for teams that otherwise struggle to break down opposing Steel-types like Mega Metagross, Ferrothorn, and Mega Scizor.