Swampert

Swampert is a very sturdy physically defensive Pokemon thanks to its great typing and bulk, which allows it to match up well against a lot of common Pokemon in the metagame like Mega Aerodactyl, Cobalion, and Bisharp. Its typing also gives it a resistance to Stealth Rock, which in combination with Leftovers further boosts its sustainability and gives it the opportunity to switch in often and set up Stealth Rock or whittle down the opposing team with Toxic. Swampert's edge over the other defensive Ground-types in the tier lies in its decent offensive stats and access to Scald, allowing it to threaten common Ground-immune Pokemon like Rotom-H and Moltres more easily as well as giving it the ability to run a fully offensive set. Access to moves like Roar can also prove to be a nuisance for Pokemon like Scizor and Dragon Dance Mega Altaria that could try to take advantage of Swampert. However, Swampert has a hard time checking the Pokemon it's supposed to like Zeraora, Infernape, and Nihilego, as they usually carry Grass-type coverage. Swampert also lacks any form of reliable recovery, which means that it's prone to being worn down if not used carefully. These aforementioned traits mean that Swampert faces heavy competition from Hippowdon and Gligar, which have access to reliable recovery and don't have to face the constraints of the Water typing, so they're much more consistent answers to the aforementioned threats.