Diancie

Diancie has one of the best offensive typings in the CAP metagame and is commonly seen taking advantage of its high offensive stats, gaining a boost of 60 to both its base Attack and Special Attack when it Mega Evolves. This makes Mega Diancie capable of running a mixed set rather than a fully physical or special one. In addition to its amazing typing and offensive stats, it has an outstanding movepool, with amazing STAB moves such as Diamond Storm and Moonblast and Earth Power to hit Steel-types. Furthermore, Mega Diancie also has some excellent setup moves, most notably Rock Polish, which allows it to outspeed common weather sweepers after a single use.

One of Mega Diancie's main drawbacks is its terrible HP stat. While Diancie does have incredible Defense and Special Defense, its HP, in a way, negates those stats. In addition, it has an awful base 50 Speed before Mega Evolving. Furthermore, its typing is pretty mediocre defensively, with a quadruple weakness to Steel as well as weaknesses to Water, Ground, and Grass, limiting the number of Pokemon that Diancie can actually switch into and making it more susceptible to common priority moves such as Aqua Jet and Bullet Punch.