Gyarados

Gyarados has several traits that make it a solid choice in GSC UU: an unusual typing that grants it useful STAB attacks and resistances, the uncommon combination of high Attack and high Special Defense, and a unique and varied movepool. Its immunity to Spikes and Earthquake is great in a metagame where Ground-types such as Nidoqueen and Piloswine are common, and its resistance to Water alongside its access to Thunder makes it a solid check to the tier's prominent Water-types such as Slowbro and Blastoise. Moreover, its coverage and bulk make it an adequate check to Scyther and allow it to do just enough damage to the tier's bulkier foes that it can sometimes be difficult to deal with. What prevents Gyarados from being a top-tier Pokemon is its crippling weakness to Electric-type attacks, which are sadly a very common sight in the tier. Its low Special Attack stat also means that it has trouble breaking through bulkier Pokemon like Granbull and Slowking. Furthermore, if it lacks Rest or Heal Bell support, then paralysis is highly problematic, as once paralyzed it has very low chances of beating Moonlight Nidoqueen, one of the most common Pokemon in the tier.