Entei

Choice Band Entei is a solid wallbreaker that punishes conventional Fire-type answers such as Flygon, Diancie, and Suicune with a burn from Sacred Fire. Furthermore, Entei can act as a revenge killer with Extreme Speed, letting it pick off many dangerous sweepers like Cloyster, Flygon, and Sharpedo. Entei also has a great Speed tier for a wallbreaker and outspeeds key offensive threats such as Mimikyu, Obstagoon, and Xurkitree. The team compression provided by being both a wallbreaker and revenge killer, as well as sporting great natural bulk and a key Speed tier, makes it particularly sought after on sun teams. Under sun, Entei's counterplay dwindles, as once hard stops like Gastrodon, Quagsire, and Snorlax have a high chance of getting 2HKOed by sun-boosted Flare Blitz after Stealth Rock and burn. However, Entei's Stealth Rock weakness severely limits it, especially on sun teams, which generally lacks thorough entry hazard removal. Outside of sun teams, Entei faces far harsher competition from other wallbreakers, especially Darmanitan, which can afford to run Heavy-Duty Boots, is about as strong as Choice Band Entei, and can keep up momentum with U-turn.