Omastar

When looking at Omastar's stats, it seems to be just another one of many bulky Water-type attackers. However, Omastar has access to what is arguably the best boosting move in the game, Shell Smash. With this gem of a move, Omastar is able to fix its low Speed and boost its already great Special Attack stat to incredible levels in just one turn of setup. Omastar also has access to both Stealth Rock and Spikes, thus allowing it to step outside of its normal sweeping role with decent success. It can even use Shell Smash along with one of these entry hazards to make for quite the flexible Pokemon. Omastar has some very useful resistances as well, including an all-important 4x Fire-type resistance that lets it use Entei, one of the most common Pokemon in the tier, as easy setup bait.

However, Omastar is held back by a few glaring flaws that prevent it from dominating the tier. Its Speed is low; even after a Shell Smash boost, Choice Scarf Pokemon such as Rotom and Manectric can still effortlessly revenge kill Omastar and limit the damage it can do in a match. A mediocre Special Defense combined with weaknesses to common attacking types such as Grass, Electric, and Fighting makes it quite difficult for Omastar to successfully set up and pull off a sweep. Nevertheless, Omastar is a very potent sweeping threat to look out for in RU. Omastar only requires one turn to lay waste to entire teams, so tread lightly around it.