Volcanion

Water

Volcanion's unique Fire / Water typing brings several advantages to the table for Water teams. Its half Fire typing allows it to revenge kill most Grass-types that threaten Water, including Whimsicott and Serperior. It also gives Water a Fairy-type switch-in other than Empoleon. Furthermore, it effectively checks Bug-types, which are very threatening to Water teams. Its stats are generally good as well; its decent 80 / 120 / 90 bulk, decent Speed for its bulk, very high Special Attack, and good Attack make it a premier choice on Water teams. Volcanion is able to run a range of sets, such as Choice Scarf, Choice Specs, Assault Vest, and even defensive. Its Choice Scarf set provides it with Speed and allows it to revenge kill Mega Diancie, Gengar, Serperior, and Galvantula. Its most powerful set, Choice Specs, makes it a threatening wallbreaker that is able to break past defensive Grass cores with Fire Blast. It's also immune to Will-O-Wisp and functions as a Scald switch-in thanks to Water Absorb, providing great support for its teammates. One of its most notable traits is its ability to 2HKO Mega Venusaur, which walls Water teams.

However, Volcanion is quite slow and is outsped and threatened by Hydreigon, Gyarados, and Mamoswine; even with a Choice Scarf, it's outsped by Mega Lopunny and Mega Manectric. It also can't take full advantage of its good Attack stat due to lacking a physical Water-type STAB move, and it's weak to common attacking types in Electric, Rock, and Ground. Due to lacking reliable recovery, it can get worn down very easily. Finally, it is weak to Stealth Rock and therefore requires Defog and Rapid Spin support if it wants to switch in and out more often.