Tyranitar

Tyranitar looks like a great Pokemon at first glance. It's the only viable setter of sand, and it has an extensive movepool and considerably high attacking stats. However, Tyranitar is, simply put, a lackluster Pokemon in DOU; its bad typing leaves it susceptible to a vast majority of common threats, such as Landorus-T, Keldeo, and Amoonguss. Furthermore, as Rock-types, Mega Diancie and Terrakion are generally the better pick with their immediate high Speed and more powerful STAB moves. Tyranitar also faces competition as a Dark-type from the likes of Bisharp and Hydreigon, which aren't totally beaten by Landorus-T and are able to fit on a wider range of team styles. Tyranitar's main saving grace is its ability to set sand, which, despite being the main part of a generally inconsistent team style, can be used to support an adjacent Excadrill and break a foe's Focus Sash. Tyranitar can also become a threatening sweeper when Dragon Dance is used in tandem with its decent STAB coverage, but it is so slow that it can't even outspeed Choice Scarf Landorus-T, its most threatening and most common foe, after a boost.