Entei

"It is said that when it roars, a volcano erupts somewhere around the globe." Such is the flavor text for Entei, a mighty force in the UU metagame--it sports one of the highest Attack stats in the tier. That's not all, either; tack on STAB Flare Blitz, priority in Extreme Speed, and a coverage move in Stone Edge, and you have got one difficult Pokemon to counter. Unfortunately, Flare Blitz and Extreme Speed are event moves, and Entei is forced to use an Adamant nature, which means it won't be outspeeding a lot. Aside from its physical attacking prowess, Entei has access to Calm Mind, and its high base HP means it can create 101 HP Substitutes, which are unbreakable by Seismic Toss. Besides what has been mentioned already, Entei's movepool isn't anything spectacular, but it has everything it needs to succeed in UU. Being a Fire-type, however, Entei is weak to Stealth Rock, and it can't stand up against common Water-, Rock-, and Ground-types moves, so provide it with proper support to get the most out of it.