Sableye

Sableye's increased bulk and incredible ability, Magic Bounce, after Mega Evolving let it switch into almost every entry-hazard setter in the Uber tier. With its ability to keep Stealth Rock and Spikes off the field, along with its amazing typing that makes it immune to Normal-, Fighting-, and Psychic-type attacks and only weak to Fairy-type attacks, Mega Sableye carves itself a large niche. This, along with its great supporting movepool, allows Mega Sableye to be a reliable stop to dangerous physical attackers such as Extreme Killer Arceus, Deoxys-A, Mega Mewtwo X, and Mega Kangaskhan. Mega Sableye can also cripple or completely halt many support Pokemon found on more defensive teams, such as defensive Yveltal, Klefki lacking Dazzling Gleam, Tyranitar, Lugia, and Ferrothorn. On the other hand, two popular Stealth Rock users, Primal Groudon and Dialga, can overpower Mega Sableye with their powerful STAB attacks, so it cannot always reliably keep Stealth Rock off the field by itself. Mega Sableye is also complete setup fodder for powerful special sweepers and wallbreakers such as Geomancy Xerneas, Darkrai, and Calm Mind Primal Kyogre, and it loses to some of the tier's most powerful physical wallbreakers: offensive Primal Groudon, Mega Salamence, Ho-Oh, and Rayquaza. Overall, with proper team support Mega Sableye is incredibly hard to pin down and beat and offers a few very rare and sought-after roles on defensive teams.