Latios is one of the strongest sweepers in the entire Ubers tier. His signature item, Soul Dew, boosts his already great Special Attack to stupendous amounts, allowing him to OHKO or 2HKO near anything with the correct move. Soul Dew also grants him a special defense boost, meaning that he can easily switch in to non-super effective special hits (as well as the ubiquitous Earthquake courtesy of Levitate) to easily set up or just KO something with his astonishingly powerful Draco Meteor attack. Latios also outspeeds a huge portion of the Uber metagame, which just makes him even more of a threat.
Despite his great power, Latios is not perfect. His typing afflicts him with weaknesses to common Uber attacking types such as Ghost-, Dark-, Dragon-, and Ice-type attacks. That Dark-type weakness makes him vulnerable to Pursuit, meaning that he is easily removed by trappers such as Scizor and Tyranitar. He also won't be getting past Blissey anytime soon either. Furthermore, he has to compete with Latias often for a team slot, as his sister is usually easier to fit in a team thanks to her superior bulk. Despite these flaws, Latios is still a great Pokemon to consider using in any Ubers team.
Latios is an amazingly powerful sweeper in the Uber environment. After a single Calm Mind, Latios reaches a jaw-dropping 808 Special Attack stat, and is capable of OHKOing or 2HKOing most of the commonly seen Uber Pokemon. This combined with a base 110 Speed stat gives you one frightening sweeper.
Dragon Pulse is a crushingly powerful attack, 2HKOing literally any Pokémon who is not Blissey or a Steel-type. Grass Knot's Base Power climbs to 120 against Kyogre and Groudon, easily OHKOing them both. Grass Knot also 2HKOes Tyranitar, a popular counter to this set. Thunder is also an excellent option over Grass Knot, if one does not fear Tyranitar. Thunder allows Latios to OHKO Lugia and most Scizor, Ho-Oh, and Forretress after Stealth Rock damage and one Calm Mind. You also have the ability to 2HKO Metagross and Heatran without any boosts at all. Most Groudon are OHKOed by Dragon Pulse after one Calm Mind as well. Recover is the preferred option in the last slot so Latios can heal himself while setting up Calm Minds. If one would prefer to OHKO Scizor in the sunlight, one may use Hidden Power Fire over Recover. However, Latios may not get as many chances to set up without Recover to help it stay alive, and the drop in its Speed IV will make it slower than other Latios lacking Hidden Power Fire. If one does not fear Kyogre or Lugia, one may use Hidden Power Fire over Grass Knot or Thunder as well.Team Options & Additional Comments >>>
This set eschews Calm Mind in lieu of being capable of posing an offensive threat right from the start. Draco Meteor is a ridiculously strong attack, as it severely hurts any Pokémon who does not resist it besides Blissey, and it is capable of OHKOing Mewtwo without any prior damage. Grass Knot easily OHKOes Groudon and most Kyogre while also doing significant damage to Tyranitar. Thunder covers Lugia, Ho-Oh, and Manaphy, and also 2HKOes most of the Steel-types in Ubers. Recover allows Latios to live longer to deal more damage. Hidden Power Fire is also a usable option, as it easily OHKOes Scizor and Forretress while giving Latios a way to reliably hurt Steel-types in the sun; however you must watch out, as the drop in Speed will make you lose to other Latios. Dragon Pulse may also used if you want a STAB attack that deals consistent damage, making Latios more usable as a late-game sweeper.Team Options & Additional Comments >>>
This set, contrary to the other Latios sets, is not based on sweeping; instead, it is based on Latios's ability to set up another Pokémon for a sweep. This set works exactly how you would think: you bring in Latios and then set up both Reflect and Light Screen. With Light Clay the two moves will each last 8 turns, including the turn in which you used it. After Reflect and Light Screen are up you have the option to use Memento, which causes your Latios to faint, but also lowers your opponent's Attack and Special Attack by two stages each. After your opponent's Pokémon is completely crippled, you're free to bring in a brand new Pokémon. In most cases, bringing in a sweeper or a Baton Pass Pokémon to set up a sweep is a good strategy.
The EVs and nature should be fairly straightforward. Timid with 252 EVs in Speed will make sure that you're fast enough to set up on most Pokémon, while the 252 HP EVs give Latios the bulk he needs to run this set. Light Clay is the best option for an item, as it greatly extends the duration of the two screens. An attacking move is used in the last slot so that Latios isn't rendered useless by a faster Taunt-user. Even with no Special Attack investment, Latios' Draco Meteor off its impressive base Special Attack stat will dent most Pokémon who don't resist it. The Special Attack drop is not too worrying as this Latios set likes to switch in and out a lot anyway. If you prefer more consistent damage, Dragon Pulse is also another STAB move that you can use, if you don't want to lower your Special Attack. Similarly, if you would like to lure in and remove Scizor, Hidden Power Fire is a usable option as well. Safeguard is also a viable option to prevent your switch-in from being hit with a status infliction.Team Options & Additional Comments >>>
Using Dragon Dance on something like Latios may seem silly at first, considering that Latios only has a modest base 90 Attack stat, but Latios can actually use Dragon Dance's Speed boost to deadly effect. After one Dragon Dance, Latios hits 525 Speed, allowing him to outspeed and KO all of his normal revenge killers—Darkrai, Mewtwo, common Choice Scarf users such as Dialga, Palkia, Kyogre, and Garchomp, and the standard Kingdra in the rain—before going on to smash through the rest of the opponent's team. With Latios's great bulk, resistances to Grass-, Water-, Fire-, Electric-, and Fighting-type attacks, and an immunity to Ground-type attacks, he isn't short on opportunities to switch in and grab a boost.
Dragon Pulse, backed by STAB and Soul Dew, will score an OHKO or a 2HKO on anything that isn't Blissey or a Steel-type. Thunder OHKOes Kyogre, Lugia, Ho-Oh, and Manaphy after they have taken Stealth Rock damage. It also 2HKOes most Steel-types, including Scizor, Metagross, Heatran, and Forretress. Hidden Power Fire allows Latios to fry Scizor and Forretress, while 2HKOing any Steel-type not named Heatran or specially defensive Jirachi in the sunlight. Grass Knot is also a viable option over Thunder, as with it, Latios will OHKO Groudon and Kyogre after Stealth Rock damage. It also 2HKOes any Tyranitar variant. However, using Grass Knot means that you lose coverage against Steel-types in the rain, so only use it if your team is centered around sunlight.Team Options & Additional Comments >>>
In the manner of EVs, usually Latios is going to want max Speed with a Speed-boosting nature, as it needs to be as fast as possible to sweep effectively. However, you can run less Speed if you want. There really is no Latios that should be used with lower than 307 Speed. In fact, Latios generally shouldn't be used with lower than 330 Speed. However, if the user feels that Palkia is no threat at all, and would like to conserve Latios' EVs and nature for something else, he/she may want to go with 307 Speed, which requires 204 EVs if Latios has a neutral Speed nature. Next is max Speed with a neutral nature (319 Speed, 252 EVs). This allows Latios to outrun maximum Speed Jolly Rayquaza and tie with other max Speed neutral Speed natured Latios and Latias. After that, one might as well go to 330 Speed, which requires 176 Speed EVs with Timid nature to outspeed a max Speed Hasty or Timid Palkia. 320 Speed does absolutely nothing but outspeed an opposing neutral nature Latias or Latios. Next is 334 Speed, which requires 192 Speed EVs with a positive nature, if one is paranoid of Garchomp in Ubers. This Speed also allows Latios to outrun a max Speed Adamant Choice Scarf Tyranitar. Latios can also outspeed a neutral max Speed Arceus with 216 EVs in Speed, putting him at 341 Speed in the stat.
Roar could work on a Calm Mind or Psych Up set, but Latias is better for that, thanks to her higher Special Defense. Heal Block looks interesting on a set with Toxic to kill Blissey, but only use this with Aromatherapy or Safeguard to keep your opponent from killing you with a Toxic of their own. Heal Block can also be used with a set that just uses brute force against the opponent (like the all-out attacker set) to keep Blissey from walling you for long. Refresh can be used on the Calm Mind set to guard Latios against status. However, when using Refresh, Latias is usually better due to her superior bulk and ability to switch into more threats.
Trick is possible with Choice Scarf, allowing Latios to become a revenge killer of sorts, especially helpful against common threats like Dragon Dance Rayquaza. Blissey will detest Choice Scarf, which could well open a sweep for the likes of Kyogre easier. However, Latios won't like being without Soul Dew.
Checks and Counters
If Blissey has Toxic, she will always beat a Latios without Safeguard, Refresh, or Psycho Shift. Even if he has Safeguard, Icy Wind can allow Blissey to get in a Toxic before Latios can refresh the Safeguard after it expires the first time. Thunder Wave Blissey can be annoying, as being fully paralyzed can spell your doom if Blissey also has Seismic Toss. Psych Up / Calm Mind Blissey with Ice Beam has a high probability of beating Latios as well.
Metagross is a great counter, thanks to its resistance to Dragon Pulse, Grass Knot, and Ice Beam, meaning that it really only has to worry about Thunder and Hidden Power Fire. It will OHKO Latios with a Choice Band Meteor Mash or a Choice Band Pursuit on the switch. Scizor works in much the same way as Metagross, though it is more vulnerable to Hidden Power Fire. Forretress can set up entry hazards against Latios if he lacks Hidden Power Fire. Bronzong can set up Light Screen to lessen the power of Latios' attacks and it can wear the Eon Pokemon down with Payback. Dark- / Bug-type Arceus can stop Latios in much the same way, but Arceus needs to be wary of letting Latios get in too many Calm Minds. Steel-type Arceus will resist a lot of Latios' attacks, much in the same way Metagross does. Tyranitar's Special Defense is boosted thanks to Sand Stream, and it OHKOes Latios with Crunch.
Deoxys-A, although incapable of switching into any offensive attack, can come in on Recover, Calm Mind, or any other non-damaging move, and OHKO with a Choice Band or Life Orb Ice Punch. Knock Off and Trick in general really hurt Latios, as Soul Dew is a major part of his success. Deoxys-D commonly carries Knock Off, and Mewtwo and Darkrai are common users of Trick.