Uxie, the tier's best check / counter to Nidoqueen and one of my personal favorites. Uxie is the prime example of a versatile Pokemon. It's got great defenses, great support moves, a decent offensive movepool, and enough Speed to even sweep. Although support is the first thing that will cross a player's mind when they see Uxie, sweeping shouldn't be out of the question:
Uxie @ Leftovers
EVs: 96 HP / 196 SAtk / 216 Spd
Timid Nature (+Spd, -Atk)
- Calm Mind
A SubCM set fits Uxie very well as it takes advantage of the pixie's great bulk and status as a solid wall / tank in RU. Uxie finds it easy to setup on many support Pokemon such as Slowking, Tangrowth, Smeargle, and even opposing supportive Uxie. With Sub up, Uxie is free to setup Calm Minds to boost both of its special stats and making its Subs nearly impossible to break on the special side. Psychic and Thunderbolt give Uxie the best overall coverage in RU, leaving it walled by the fewest possible common threats. Note that the Speed EVs allow Uxie to outrun positive natured base 90 Speed Pokemon which most notably includes Moltres. This is major as it allows Uxie to come in, setup a CM, and still survive the 2 Fire Blasts it would take (one switching in and one after CM) with the given HP EVs.
Uxie really wants entry hazards to limit the amount of Calm Minds it needs to successfully sweep. Smeargle, Steelix, Qwilfish, and Accelgor are good hazard users. Steel types are a pain, primarily Steelix as it literally doesn't care about Uxie at all, no matter the set the pixie runs. This one is no different, so strong, bulky special attackers such as Rotom-C and Tangrowth are solid teamates. Fighting types in general help since they can switch in on Pursuit. Gallade, Hitmonlee, and Medicham can all work. They also pummel Steel types. Magneton is a more direct answer to rid the opposing team of Steel types, but it will struggle against Steelix.
Uxie has many other sets it can use thanks to its great stats. A standard support set having SR, Psychic, and some variation of U-turn, Memento, Thunder Wave, Heal Bell, and Yawn is the first that comes to mind as the bulky spread the set typically uses allows Uxie to effortlessly handle Nidoqueen, one of the tier's top special attackers, as well as many other opponents that fail to hit Uxie for super effective damage. Dual Screens is another approach as Uxie's bulk and Speed make it the best user in the tier. It can even setup SR or use Memento alongside Screens.
An anti-lead set with Lum Berry and max Special Attack and Speed can really screw over many common responses to Uxie and allow the pixie to handle the likes of Lilligant and Smeargle with greater ease. Finally, weather support shouldn't be overlooked (Texas already covered that) as Uxie's great bulk and access to Memento make it one of, if not, the best weather setters in the tier.