Latias

Latias is the only Dragon / Psychic type in the tier, which means that it's an answer to Fighting-, Fire-, Water-, Grass-, Electric-, and Psychic-types. The combination of all these resistances is unique to only Latias and allows it to answer potent wallbreakers like Infernape and Breloom, which very few Pokemon can do. Furthermore, it's completely immune to Spikes and Toxic Spikes thanks to Levitate, and it's also not weak to Stealth Rock, which means it's more resistant to all entry hazards than most Pokemon. Latias has such a vast array of move options that it can perform many different roles. With all these traits, Latias boasts near-unparalleled role compression, allowing it to fit wonderfully on almost any team and pair well with almost every Pokemon individually. Its stats are also nothing to scoff at, with monstrous Special Defense as well as impressive Special Attack and Speed.

The main thing that holds Latias back is its susceptibility to Tyranitar, which can switch in, take Latias's Draco Meteor or even Surf, and trap it with Pursuit while threatening a powerful STAB-boosted Crunch. Latias's presence means Tyranitar is often equipped with increased Special Defense investment, which can allow it to take even a Choice Specs-boosted Draco Meteor when healthy and still survive another one. Latias can also have a very hard time versus many Steel-types like Jirachi, Bronzong, Metagross, Empoleon, and even Magnezone, which can take a Draco Meteor or Surf decently well provided that Latias doesn't hold Choice Specs. Even if Latias forces a KO with its strong Draco Meteor, Tyranitar can easily revenge kill it, or another Pokemon can take advantage of Latias's lowered Special Attack. Besides Tyranitar and Steel-types, bulky special walls like Blissey and Clefable can take any attack and have high potential to force Latias out with the threat of a status move or chip damage from Seismic Toss and Ice Beam.

It's not all black and white, however, because Latias's astronomical movepool enables creativity and counterplay to its common checks with moves like Trick and Thunder Wave. While Latias cannot avoid its biggest flaw, which is its susceptibility to some of the top threats in the OU metagame compared to other Pokemon, it has so many positive attributes that it's a fantastic fit on almost any team.