Flygon

UU isn't a very kind metagame to Flygon. While it is a very versatile Pokemon with access to great STAB attacks including Outrage and Earthquake, a good typing and ability that allow it to freely switch into Ground- and Electric-type attacks, and a good Speed tier of base 100, it is easily countered by many different Pokemon. Flygon's main drawbacks are its mediocre bulk and 4x weakness to Ice, making it very susceptible to attacks such as Ice Shard and Ice Beam. In addition, its Attack is underwhelming, and it relies heavily on Outrage to break through bulkier Pokemon. It also faces stiff competition from other Pokemon such as Hydreigon offensively and Gligar defensively. Though Flygon may seem to have many positive attributes, its drawbacks make it a very niche choice in the current UnderUsed metagame, and there will almost always be a superior choice.