Diancie

Mega Diancie is a superb Pokemon in OU thanks to its solid Speed and attacking stats, STAB combination, coverage moves, support movepool, and Magic Bounce ability. Mega Diancie's typing and ability allow it to set up Stealth Rock in the face of entry hazard control options such as Tornadus-T and Zapdos and force out Mega Sableye with Moonblast. Additionally, the combination of Substitute and Endeavor allows it to shine as one of the most consistent leads for hyper offense teams, as Magic Bounce allows it one turn to set up Stealth Rock and deny hazards before going down. Mega Diancie's typing also lets it check troublesome Fire-types such as Volcarona and Victini in a pinch. Diancie also has the option to delay Mega Evolving so that it can make use of its better bulk to more easily handle attacks from Pokemon like Heatran. However, Mega Diancie is burdened with a poor HP stat, and its typing leaves it riddled with a crippling 4x weakness to Steel, as well as weaknesses to common offensive types such as Ground, Water, and Grass. Additionally, it is outpaced and immediately threatened by common Pokemon such as Greninja, Serperior, Tapu Koko, and Choice Scarf users like Kartana and Landorus-T. Offensive Mega Diancie also cannot fit all of the coverage and utility options it wants into one set, while the lead variant must choose between Diamond Storm to threaten Volcarona, both Mega Charizard formes, and Calm Mind Tapu Koko or Moonblast to threaten Dragon-types and Mega Sableye.