Ferrothorn

Ferrothorn's reasonable 74 / 131 / 116 bulk and many resistances allow it to act as a reliable check to many specific threats, including Poison Heal users such as Primal Kyogre, Regigigas, and Xerneas, as well as check a variety of other Pokemon such as Mega Diancie, Sheer Force Mega Mewtwo Y, and Zekrom. Ferrothorn has a niche over the bulkier Registeel and other Steel-types mainly thanks to its Grass typing, which offers a neutrality to Ground-type attacks, a resistance to Water and Electric, and a key immunity to Spore that other Steel-types must forego another item to gain through Safety Goggles. Ferrothorn also benefits from its lower Speed stat, which helps with slow pivoting and utilizing Core Enforcer to suppress abilities. In addition to its many resistances, Flash Fire is used to remove the 4x weakness to Fire, which is a common coverage type for Pokemon such as Mega Diancie and Xerneas. Thanks to its dual typing, Ferrothorn can check some Zekrom and Primal Kyogre sets, which other Steel-types struggle with. The main drawbacks of Ferrothorn are the competition it faces from Registeel due to Registeel's higher bulk and its lack of Ice and Flying resistances, which limits its use in checking most Mega Diancie sets and Kyurem-B, an otherwise common role for Steel-types. Its lower bulk, while mitigated by resistances, does limit Ferrothorn's ability to take hits from wallbreakers that can hit it neutrally such as Adaptability Mega Gengar and Mega Garchomp. Also, Ferrothorn suffers from being predictable due to almost always needing Flash Fire to avoid OHKOs from common Fire-type coverage moves.