Smogon official tier: OU
Base Stats: 80 HP, 90 Attack, 80 Defense, 130 Sp. Attack, 110 Sp. Defense, 110 Speed
“Usable” moves (according to Pokémon Showdown): Aerial Ace, Body Slam, Calm Mind, Charge Beam, Double-Edge, Draco Meteor, Dragon Claw, Dragon Dance, Dragon Pulse, Earthquake, Energy Ball, Façade, Frustration, Grass Knot, Hidden Power (Electric, Fighting, Fire, Grass, Ice), Hone Claws, Ice Beam, Light Screen, Magic Coat, Memento, Outrage, Protect, Psychic, Psycho Shift, Psyshock, Rain Dance, Recover, Reflect, Refresh, Rest, Return, Roar, Roost, Shadow Ball, Shadow Claw, Sleep Talk, Solar Beam, Substitute, Sunny Day, Surf, Tailwind, Thunder, Thunder Wave, Thunderbolt, Toxic, Trick, Waterfall, Zen Headbutt
(Note: even though it’s not listed, Defog is also a viable move)
Latios is best compared to his twin sister, Latias (who has the same typing and 80/80/90/110/130/110 stats). Anyone who decides to use Latios should realize that he’s more offensively tailored than his twin sister, so his moveset should be considered accordingly. Support options like dual screens and Defog are more worthwhile in the possession of the sister, Latias (although that’s not to say they’re not viable). That is why all of the bolded moves are offensive.
Here is the set I like to use:
Latios (M) @ Choice Specs
EVs: 4 HP / 252 SpA / 252 Spe
IVs: 0 Atk / 30 SpA / 30 Spe
– Dragon Pulse
– Hidden Power [Fire]
I had Draco Meteor over Dragon Pulse initially, but I came to realize that Draco Meteor makes half of the moveset Pursuit bait for Bisharp. Not to mention it eases prediction of Ferrothorn switch-ins after the Specs are tricked away. Hidden Power Fire is mainly there for Steel-types like Ferrothorn, Scizor, and Forretress, who would wall the set otherwise (especially Mega Scizor, who can’t be tricked). Psyshock hits special walls like Chansey and Fairy-types like Togekiss for more damage than its other moves. Trick is the defining trait of this set, which allows Latios to pass his Specs and potentially neuter a physical attacker or a wall. Choice Scarf can also be considered, but it can be costly when put into the wrong hands.
Now, here is a more common set:
Latios (M) @ Life Orb
EVs: 4 HP / 252 SpA / 252 Spe
IVs: 1 Atk / 30 Def / 30 SpA / 30 SpD / 30 Spe
– Draco Meteor
– Hidden Power [Fighting]
Life Orb Latios is the only variant of Latios I’ve seen apart from mine, so I decided to take a look at the Smogon Strategy Pokédex and see what it had to offer. Draco Meteor is Latios’ hardest hitting move and is not as problematic for a Life Orb set as it is for a Choice set (because you have the ability to use a non-attacking move after). Psyshock is there for the same reason as the Choice set, and Hidden Power Fighting makes it even harder to Pursuit trap. Now, on the Strategy Pokédex entry, I saw that they recommended Roost as a fourth move. Why Roost? If you’re a Levitating Pokémon and have the choice between Recover and Roost, there is literally no reason to choose Roost. Anyway, the recovery move is there to restore the HP it lost via Life Orb and other prior damage (and, as I mentioned before, it can be used as an alternate option instead of switching after using Draco Meteor).
Other options: Once again, it can use supporting options like Defog and dual screens, but those are better off with Latias. Thunderbolt is an option for hitting Togekiss and Azumarill harder than anything else. Substitute can be used to block status, scout for Pursuit or Sucker Punch, and ease prediction in general. Dragon Dance is an okay option (mainly for the surprise factor, if anything), but I wouldn’t recommend it.
I will include a team, but take it with a grain of salt because it has not passed 1300 in rank (added to the fact that it has no hazard control): http://pastebin.com/xgJsicLE