Raikou

Raikou is one of two viable mono-Electric-type Pokemon in OU, alongside Jolteon, which gives it a unique niche. Its Speed tier is incredibly desirable, getting the jump on Pokemon like Infernape, Latias, and Gengar with a Speed-boosting nature and Speed tying with Starmie; even with a neutral nature, it just barely outspeeds all base 100 Speed Pokemon like Jirachi, Flygon, Zapdos, and Shaymin. Its very good special bulk makes it a fantastic offensive answer to Pokemon like Zapdos, Gengar, and even Starmie. In particular, Raikou shrugs off all of Zapdos's attacking moves thanks to its good typing and Special Defense. Raikou also has access to Aura Sphere, which can go as far as OHKOing many variants of Tyranitar; this is something that very few special attackers can do.

Despite its positive traits, Raikou has quite a few shortcomings that prevent it from dominating the OU landscape. If it runs Aura Sphere, it must run a Rash nature, which not only prevents it from outspeeding Infernape, Latias, and Gengar but also reduces its Special Defense considerably. Ground-types like Hippowdon and Swampert can completely shut down Raikou, and if it uses Hidden Power Grass to catch Swampert, it will be much worse versus other Ground-types like Flygon and Gliscor. Raikou doesn't have a reliable healing move and has subpar Defense, so it's vulnerable to physical attacks, detests status, and often sees its use limited by sand.