Hydreigon

In the earlier years of VGC, Hydreigon was considered nearly uncounterable, yet it now has a difficult time maintaining this status. Hydreigon gained a 4x weakness with the introduction of Fairy-types, and consequently, it now has a harder time staying alive; its base 98 Speed, which falls short of the 100 base Speed tier, is even more problematic than it was in the last generation. Its Dark typing also brings extra Fighting- and Bug-type weaknesses to the table, including weaknesses to many priority moves such as Mach Punch. On top of all this, it's not the only Dragon available; Hydreigon faces stiff competition from faster and bulkier Dragons, including old rivals such as Salamence and Garchomp, as well as newer Dragons such as Noivern and Goodra.

However, don't count Hydreigon out just yet. Thanks to its base 125 Special Attack stat, Hydreigon is the strongest specially-based Dragon in the metagame. Hydreigon is also able to hit Steel-types with its STAB moves, as Dark-type moves are no longer resisted by Steel-types, giving it great coverage alongside its Dragon-type attacks. Its typing and Levitate ability also give it immunities to both Ground- and Psychic-type moves, which combined with its above average 92/90/90 bulk and slew of resistances means it can take an attack or two along the way. Finally, Hydreigon is quite versatile and has a vast movepool, allowing it to run a physical or even mixed set to surprise its opponent if need be. Even though it's slower than its Dragon brethren, Hydreigon's raw power will not disappoint.