Omastar

Omastar is widely regarded as one of the best Pokemon in UU due to its excellent defensive and offensive qualities. Omastar's access to Spikes is incredibly important for virtually every playstyle, and it finds itself to be the easiest Spikes setter to fit on teams due to its great Defense and decent defensive typing in Water / Rock, which gives it useful resistances to Flying- and especially Normal-type moves; these traits also make it one of the best leads in the metagame and a solid check to powerful Pokemon like Scyther, Fearow, and Kangaskhan. Additionally, Omastar's sky-high Special Attack prevents it from being completely passive when running defensive sets, threatening most of the Pokemon it checks with a strong, STAB-boosted Surf, and allows it to become an extremely deadly rain sweeper when paired with Swift Swim that can completely decimate teams once its checks have been taken down. However, while Water / Rock does provide some handy resistances, it also gives Omastar very common weaknesses to Grass-, Electric-, Ground-, and Fighting-type moves, making it more difficult for it to consistently check Pokemon like Choice Band Granbull and Kangaskhan and lessening its effectiveness as a check to Fire-types like Ninetales, since they often run Grass-type coverage. Omastar also suffers from poor special bulk, meaning strong neutral or super effective special attacks will often severely cripple or outright KO it. Omastar's lack of reliable recovery and vulnerability to status don't help it either, since Leftovers can instantly be negated by poison or burn and offensive sets detest being paralyzed due to their reliance on outspeeding foes. Omastar is also extremely slow without Swift Swim, so it often must take a hit before it can do anything.