Steelix

Steelix is one of the best defensive Pokemon in the tier due to its great defenses, ability, and typing enabling it to check a wide range of Pokemon such as Heliolisk, Sneasel, Aerodactyl, Vivillon, and Comfey. Steelix is also a great Stealth Rock setter because of this, using its top-quality defensive traits to switch in multiple times if needed to set entry hazards. Unfortunately, Steelix is vulnerable to a wide variety of common Pokemon such as Slowking, Alolan Exeggutor, and Delphox due to its typing and below-average special bulk, and its passivity means it can be exploited by certain setup Pokemon such as Scrafty and Sigilyph as well as other entry hazard setters in Weezing and Seismitoad. Furthermore, Steelix struggles to reliably set Stealth Rock against teams with Xatu, relying on Curse to have any chance of threatening it, as well as Blastoise, which can easily switch into Steelix and force it out.