Tyranitar

Thanks to its excellent stat distribution, unique typing, and wide movepool, Tyranitar is a key Pokemon in GSC OU. Most notably, a combination of a strong Pursuit, solid all-around bulk, an important Normal resistance, and access to Roar allows Tyranitar to provide very desirable role compression for teams looking for a Pokemon able to check threats such as Snorlax, Gengar, Exeggutor, Misdreavus, and Jynx all at once. These factors make Tyranitar very easy to fit on teams, as the sheer utility of Pursuit and Roar is extremely helpful in the metagame. Furthermore, Tyranitar is a versatile Pokemon that can turn into a Curse sweeper that invalidates typical answers to Curse Snorlax such as phazing and Explosion thanks to Roar and its part-Rock typing. Tyranitar is also capable of acting as a lure due to its numerous coverage options that allow it to dent its usual answers.

However, Tyranitar doesn't have access to a powerful STAB attack to fully exploit its tremendous base 134 Attack stat. Therefore, it faces competition as a physical attacker from Rhydon and, to a lesser extent, Golem. Moreover, Tyranitar suffers from several common and exploitable weaknesses, a below-average Speed stat, an unfortunate case of four-moveslot syndrome, and a tendency to be unable to punish switch-ins from dangerous Pokemon such as Nidoking, Marowak, Vaporeon, Rhydon, and especially Machamp. These flaws also hamper its overall reliability against the threats it is supposed to keep in check, seeing that it struggles to pressure Starmie and takes substantial damage from Exeggutor's Giga Drain, Gengar's Dynamic Punch, and most importantly, Snorlax's Earthquake, meaning Umbreon provides serious competition, as it usually performs better against these examples. Finally, Tyranitar usually has to check multiple Pokemon throughout the match and can be worn down fairly quickly when factoring its weaknesses, lack of reliable recovery, and susceptibility to residual damage in the form of Spikes and Toxic.