I can't believe no one has done this beast...
Role: Special Sweeper, Late Game Cleaner
What it does: What doesn't it do is the question here. Blessed with a base Speed Pokemon would give an arm and leg for, Tornadus-T has really risen to becoming the best genie out there. It can scout using U-Turn, prevent hazards from being set with Taunt, Spam mindless Hurricanes and U-Turn out if the situation is unfavorable, poke holes in the opponents team, and sweep late-game once it has outlived its counters and checks. Tornadus-T is a Pokemon that is not confined to one role. It accels in many areas whether it be cleaner, Special Attacker or Scouter.
Good Teammates: The Frog of the Ages, Politoed. Thanks to all of that swaggy Rain and Drizzle that it brings, Torn-T is able to fire of LO STAB Hurricanes with a base 110 SpA...not too shabby.
Torn-T really appreciates Pokemon that are able to soak in Ice, Rock and Electric type moves and that are also able to draw out Fighting Types and Grass Types. Keldeo, Jirachi, and Ferrothorn are pretty good candidates. Keldeo can run right through Special walls with Secret Sword and also benefits from Rain. Jirachi can take Ice Shards and Stone Edges and Volt Switches if it must. Jirachi can also act as a Specially Defensive Pivot setting up Rocks and U-Turning to Tornadus when Ground Type moves start appearing. Ferrothorn is able to set up hazards turning some 2HKOs into crucial OHKOs.
What Counters it: Well...Jirachi and Heatran can be "counters" I guess...TBH they aren't really true counters as Torn-T will end up out-living them or simply hitting them with an appropriate move at the right time. Torn-T does have checks though. Scarf Thundurus-T, Scarf Keldeo, Scarf Starmie, Scizor, Mamoswine, Weavile, Scarf Latios, and Scarf Landorus are some threats that come to mind that are able to scare out or KO Tornadus-T.
Additional Info: This Pokemon is very difficult to deal with in its ideal conditions. It is a Pokemon that is able to do massive damage output and receive little consequence if the player mispredicts.