Quagsire

With a solid defensive typing in Water / Ground, Quagsire has valuable resistances to Fire-, Rock-, Steel-, and Poison-type moves, on top of an Electric-type immunity and only one weakness, albeit a 4x one to Grass-type moves. While 95 / 85 / 65 defenses are on the middling side of decent, especially concerning Special Defense, it's just enough for Quagsire to survive a wide range of physical and special attacks that are not Grass-type, using Z-Stockpile's healing effect to immediately negate any attack that doesn't KO it and boost its defenses. Access to Unaware means that foes like Mega Charizard X and Landorus-T can't use boosting moves of their own to counter Stockpile, leaving them unable to KO Quagsire with an attack. However, Quagsire's average bulk can be taken advantage of by some of the more powerful moves in 1v1, and it can still be easily OHKOed by some of the most common Pokemon in the game, such as Greninja, Tapu Lele, and Porygon-Z. Stockpile can only be used three times as well, meaning moves that drop defenses such as Metal Sound can leave Quagsire vulnerable. Quagsire is also very passive, struggles against opposing stall like stall Deoxys-S and Rest Slowbro, and tends to lose to Taunt from Pokemon like Mega Gyarados and Kommo-o.