Eternatus

Eternatus is one of the big three threats in Ubers due to its ability to check Yveltal, causing it to be found on the vast majority of teams. Additionally, it's the premier Kyogre check thanks to its typing, great bulk, Speed, reliable recovery, and access to strong damaging and support moves. It also provides important role compression and soft checks a variety of threats, most notably Ho-Oh and Marshadow. Eternatus is also an offensively threatening Pokemon in its own right with its high offensive stats, backed by strong attacks such as Dynamax Cannon, Sludge Bomb, Flamethrower, and Meteor Beam. Eternatus is one of the best poison spreaders around with access to Toxic, Toxic Spikes, and Sludge Bomb; it is also immune to Toxic and clears opposing Toxic Spikes. Although Pressure is a mostly useless ability, Eternatus does at least have the attributes to realistically PP stall when utilized on defensive teams. Simply put, Eternatus is a highly customizable Pokemon that can adapt its moveset, item, and EV spread to accommodate its team's weaknesses. However, apart from a Water-type resistance and Toxic immunity, its defensive typing isn't great; it takes heavy damage from Psychic-, Ground-, Ice-, and Dragon-type moves, which are all fairly common.