Dialga

Dialga is a slow powerhouse that has good offensive stats and decent defensive stats, allowing it to run both offensive and defensive sets. With an offensive set, Dialga can pressure the opponent with STAB Doom Desire and wallbreak late-game with Tail Glow boosts, setting up on various Steel-types, Water-types, and slow Pokemon like Mega Audino. Because Dialga isn't weak to Fire, it doesn't feel obliged to run Flash Fire on its sets like other Steel-types, giving it the option to run other abilities instead. Defensively, its RegenVest set easily fits onto many team archetypes because it can remove entry hazards, steal boosts with Spectral Thief, disable the foe's ability, paralyze the foe, and most importantly, pivot out. Also, thanks to its Steel / Dragon typing, Dialga serves as a nice check to many top threats in the metagame, namely Mega Mewtwo Y, Primal Kyogre, and Normal-types. The efficacy of these sets, however, depends also on the level of support Dialga can get from its teammates. Its offensive sets require a lot of support due to how easily they can be revenge killed. When using Dialga, you should always be wary of Fighting- and Ground-type attackers like Mega Mewtwo X and Red Orb Groudon and should play accordingly. Pokemon with common Ground and Fighting coverage such as Precipice Blades Mega Diancie and Secret Sword Mega Mewtwo Y can threaten Dialga. Also, Dialga's offensive sets are hindered by the passive mechanics of Doom Desire and Dialga's relatively slow base 90 Speed. Despite all this, Dialga still manages to be extremely useful in the right circumstances and should not be underestimated.