Hydreigon

Hydreigon is a threatening special attacker in Battle Spot Singles. Hydreigon's STAB combination is incredibly difficult for most Pokemon to switch in, with Dark Pulse hitting Psychic- and Ghost-types, such as Mega Metagross, Mega Gengar, and Aegislash, while Draco Meteor deals heavy damage against anything that doesn't resist it. This typing along with its ability Levitate and passable bulk make it an excellent check to Ground-, Ghost-, Psychic-, Electric-, Water-, Fire-, and Grass-types, including, but not limited to, Landorus-T, Aegislash, Heatran, Mega Charizard-Y, and Thundurus-T. It has access to coverage moves that can deal with Pokemon that resist its STAB moves, with Fire Blast and Flamethrower for Steel-types, Earth Power specifically for Heatran, and Flash Cannon for Fairy-types.

Unfortunately for Hydreigon, its typing gives it weaknesses to Fighting-, Bug-, Dragon-, and Ice-types along with a 4x weakness to Fairy-types, the latter of which resists Dark Pulse and is immune to Draco Meteor. This leaves it weak to common Pokemon such as Mamoswine, Mimikyu, Tapu Lele, Tapu Koko, Garchomp, Mega Salamence, Blaziken, Pheromosa, and Volcarona. Its speed, while far from terrible, leaves it outsped by Pokemon with base 100 Speed as well as most Choice Scarf users if not carrying one itself.

Below are some sample sets. These sets are likely to be standard, but they will be expanded upon and updated as the metagame progresses.