At first glance, Tornadus's Incarnate forme appears to be outclassed by its Therian form, as Tornadus-T has better bulk and higher Speed. However, normal Tornadus has access to the incredibly useful Prankster and Defiant abilities, as well as better Attack and Special Attack stats. Even though it's slower than its Therian forme, Tornadus still has a blistering fast base 111 Speed and can outpace most of the metagame. Furthermore, access to an incredibly powerful STAB Acrobatics allows Tornadus to deal major damage to any Pokemon that doesn't resist it.
Tornadus didn't get much love after the VGC 2011 season ended. Intimidate's popularity took off, Tyranitar and Metagross were (and still are) everywhere, and because of its one-dimensional coverage, which consisted of Acrobatics and... Acrobatics, a lot of teams could easily handle Tornadus without going out of their way. However, with the release of its Dream World ability, Defiant, and the addition of Superpower to its movepool courtesy of BW2, Tornadus found its way into more teams. While it still has issues with old foes, Tornadus remains as a great pick to offset the influx of Intimidate spam goodstuffs, or just Fighting-types in general.
Behold the majesty of Defiant Tornadus. This set boasts a whopping 165 Base Power STAB move, utility with Taunt and Tailwind, and of course the very real possibility that Tornadus will receive an Attack boost without having to do anything thanks to the popularity of Intimidate. Superpower picks up Acrobatics's slack, nailing troublesome Pokemon such as Tyranitar, Heatran, and Bisharp, though it is interesting to note that a Flying Gem-boosted Acrobatics hits Pokemon such as Rotom-W just as hard as a neutral Superpower would. If the Attack and Defense drops seem too risky, U-turn is perhaps a safer option. U-turn still hurts Tyranitar, softening it up for a more capable teammate to take care of it, and keeps Tornadus safe until the coast is clear and it can continue to fire off Acrobatics.
Taunt is a mainstay from its 2011 Prankster set, especially with Cresselia running around everywhere using annoying moves such as Swagger and Thunder Wave. It is also a good way to halt Trick Room setup with a little help from a Fake Out user. Tailwind is another move you might recognize. The boost it provides to Tornadus and its teammates' Speed allows them to go toe-to-toe with Swift Swim, Sand Rush, or Choice Scarf Pokemon, even if only for three turns. However, Tailwind is still, and always will be, a risky play for Tornadus as long as Trick Room and Thunder Wave remain popular, so as always, use it in moderation. Substitute is slightly less useful without Prankster backing it up, but since Tornadus outspeeds all of its threats bar Choice Scarf users and the surprisingly uncommon max Speed Thundurus, Substitute is a great move that can block troublesome Will-O-Wisps, Sucker Punches, and weakened Draco Meteors. Protect is a staple for Defiant Tornadus because the most common Intimidate Pokemon —Hitmontop and Scrafty— also carry Fake Out, which can leave Tornadus wide open and vulnerable to Rock Slides or Thunderbolts.Team Options & Additional Comments >>>
The new Defiant Tornadus might be more popular than the old Prankster Tornadus, but Prankster is by no means outclassed; in fact, against teams without Intimidate, Prankster Tornadus is arguably more useful. Priority Tailwind is useful for turning the tables on Swift Swim and Choice Scarf Pokemon and turning lumbering tanks into Speed demons. Priority Taunt is also a great move to have in the unfortunate event that Trick Room is set up and Amoonguss is threatening to Spore your entire team. It also shuts down most Cresselia, although they'll still threaten Tornadus if they have Ice Beam and Special Attack investment. Substitute can be a makeshift Protect because of priority and has the potential to linger for more than one turn, should the opponent not attack Tornadus, and also acts as a nice barrier against status moves such as Thunder Wave and Spore. However, Tornadus's Substitutes can't take more than one attack most of the time, and spread moves such as Rock Slide allow the opponent to break the Substitute without having to predict; in such cases, Protect is the superior and safer option. Acrobatics is here for obvious reasons and Superpower can round out its coverage. An offensive Prankster (pun intended) is certainly viable, though it would be best to make use of Tailwind in this case.Team Options & Additional Comments >>>
Tornadus is strapped for physical Fighting-type moves, with the only other options being Hammer Arm and Brick Break. Brick Break can help out against Light Screen Cresselia and doesn't lower your stats, but is laughably weak, being unable to OHKO Chople Berry-less Tyranitar. Hammer Arm is stronger and might seem appealing to "counter" Trick Room, but is generally a bad idea, especially since max Speed Tornadus will often need to use it twice before it's actually slower than anything on a Trick Room team. Crunch is another interesting option, as it hits the ever-present Psychic-types super effectively, but isn't worth it unless you're keen on preserving your Flying Gem, because Acrobatics will hit harder than a super effective Crunch. Other supportive moves, or more accurately moves that receive the Prankster boost, include Swagger, Rain Dance and Role Play. Swagger boosts your teammates's Attack with no side effects if they're holding a Lum or Persim Berry, or are protected by Safeguard. It also functions defensively to spread confusion to your opponent, potentially preventing huge Draco Meteors or annoying Thunder Waves from landing. Rain Dance is useful for setting up rain should your Politoed suffer a premature demise, and could be used in conjunction with Hurricane. In a similar vein to Skill Swap, Role Play allows Tornadus to copy your partner's or the opponent's Intimidate, Storm Drain, Lightningrod, Sand Stream, and for the adventurous, Contrary abilities. The main reason this isn't terribly useful is because of how situational it can be, requiring the right opponent should you lack partners with said abilities, and the fact that it doesn't transfer abilities like Skill Swap does, (for instance, you can't remove opposing Gastrodon's Storm Drain to hit its partner with a Water-type move) making it less versatile than Skill Swap.
Tornadus has a much better special movepool compared to its physical, as well as a higher Special Attack. The reason none of those are used however, is because special Tornadus is largely outclassed by its brothers, Thundurus-T and Landorus as well as other Pokemon such as Zapdos, Rotom-W, and Cresselia because of either bulk and access to Speed control or more reliable, higher Base Power moves such as Thunderbolt and Earth Power. Special Tornadus can be used to great effect, however, as long as you keep supportive moves on it and take advantage of Prankster.
Unfortunately, while Tornadus has a myriad of usable special moves, the vast majority of them don't exceed 80 Base Power. These moves are Dark Pulse, Hidden Power, Heat Wave, Grass Knot, and Icy Wind. Heat Wave is a useful spread move, considering how Tornadus hates Steel- and Ice-types, but is still weak due to the 25% power drop when hitting two Pokemon. Grass Knot can surpass 80 Base Power on Tyranitar and Terrakion, though it can't OHKO Tyranitar and has little utility outside of that. Dark Pulse isn't used for the same reason as Crunch, but in this case, it can cause timely flinches and is stronger than Air Slash when hitting super effectively. The most useful Hidden Power would probably be Ice, but it suffers from being woefully weak. Icy Wind is useful for Speed control as it trips Yache Berries and still does a reasonable amount of damage, though it doesn't get a Prankster boost while Tailwind does and accomplishes mostly the same thing, albeit only for three turns. Tornadus's most powerful special attacks, Hurricane and Focus Blast, would rocket special Tornadus to the top of its sets in terms of usage if either one was more accurate than 70% in any weather. Hurricane is still a useful option for rain teams, but again, it is outclassed by Thundurus there and rain can be cancelled in the blink of an eye with Abomasnow and Tyranitar. Air Slash is therefore the most reliable STAB, but it suffers from a horrendous 75 Base Power, which isn't enough to OHKO things it's supposed to, such as Hitmontop, though it does have a 30% flinch chance working in its favor.
Checks and Counters
Like any other Flying-type, Pokemon that resist its STAB moves and threaten it with super effective STAB moves of their own are Tornadus's natural predators. Zapdos, bulky Thundurus, and Rotom-W (as well as every other Rotom except Rotom-C) spring to mind, as the only thing that Tornadus can threaten the former two with is the rare Hidden Power Ice, and even with minimal defensive investment, it misses out on the OHKO. Tornadus can only hope for a critical hit with Superpower, should it be unfortunate enough to be left alone against a Rotom forme. Tyranitar with Chople Berry is another great check to Tornadus, as it isn't as afraid of Superpower as Dark Gem or Passho Berry variants are, and resists Acrobatics. Choice Scarf Tyranitar can straight-up outspeed Tornadus and threaten it with Rock Slide, although Jolly Tyranitar's Rock Slide misses out on OHKOing Tornadus at full health without Sand Stream damage or Helping Hand support, and Adamant Tyranitar only has a 50/50 shot at OHKOing it, which aren't exactly betting odds. Metagross can switch in on the first Acrobatics with ease, making Tornadus easier to deal with for the rest of the match, and can use Ice Punch or a simple Meteor Mash to bring it down to Bullet Punch range, or even Feint range should you have another Pokemon with it. Lastly, Tornadus hates getting burned or paralyzed; Sableye is especially good at burning Defiant variants, which are easy to pick out if you pay attention to the Poké Ball it was released from, but it has to be wary of Prankster Tornadus that use Taunt. Cresselia is the prime user of Thunder Wave, and has the option of using Ice Beam to nail cheeky Tornadus that think they can get away with simply Taunting a Cresselia. Cresselia also has the option of using Icy Wind, which can't be blocked by Taunt and can deal around 20% to Tornadus, making it easy pickings for the aforementioned Tyranitar. It should be noted, however, that by slowing Defiant Tornadus with Icy Wind, you risk an incredibly powerful Acrobatics next turn, so make sure you're able to KO it afterwards.