I'd like to petition Hydreigon to be moved from B Rank to
A Rank. Ever since Genesect came to OU, Hydreigon was given the cold shoulder in team building since Genesect could pretty much OHKO Hydreigon with two of it coverage moves, one being STAB, and what's worse is that it was on 50% of teams, which meant Hydreigon needed a lot of team support in order to get it to fulfill it's niche on a team. Although Hydreigon is still plagued with a terrible defensive typing in Dark, leaving it weak to Fighting type priority and U-Turn, Genesect is now Uber, which means Hydreigon has the ability to shine again.
What many don't seem to realize is that similar to Kyurem-B, NOTHING can really safely switch into it's moves. Hydreigon has one of the best mixed capabilities of all Dragons in the tier, and a great special/physical move pool to take advantage of it. As some of you may know, I have recently built a really successful team with a friend of mine that was centered around Hydreigon, and after countless amounts of tests and pitting my own teams against this team, I have learned that Mixed Hydreigon is one of the most terrifying things to face in OU. There's really no way to prepare for it, you just have to pray that the opponent doesn't get a free switch into you with Hydreigon. The Mixed LO set consisting of
Draco Meteor / Fire Blast / Superpower / Roost or Earthquake or Dark Pulse can hit pretty much the entire OU tier for super effective damage or extremely hard. The goal of this set is to lure in obvious counters and checks such as Blissey, Heatran, and Mamoswine, and being able to OHKO back with the right coverage move. Both the pink blobs and Max HP Heatran are comfortably 2HKOed by Superpower (Chansey is possibly 3, but fuck Chansey), while Standard LO Mamoswine is OHKOed after rocks (and yes he can tank an Ice Shard even after SR). Hydreigon can still use Draco Meteor on the predicted Forretress, Scizor, and Ferrothorn switch and still OHKO them all with a -2 Fire Blast while having a decent chance of OHKOing the latter after Stealth Rocks. That's quite amazing, which shows that not even Steel types can safely switch into Hydreigon. The only hard counter that I've seen who can switch into any of it's moves, is SpD Jellicent, because it's immune to Superpower, is 3HKOed by Draco, and resists Fire Blast. Other than that though Hydreigon is extremely hard to switch into. If the opponent gets a free switch with the Hydreigon, your most likely going to have to sack something. It's quite easy to get free switch momentum with Hydreigon anyway since he forces so many switches.
All in all, Hydreigon may not be the fastest and best Dragon defensively, but offensively he is one of the most dangerous dragons in OU, and easily defines the word "uncounterable".
Unlike most Dragons, he needs little team support to be effective, and can easily threaten anything even at the very start of the battle. With the vast amount of sets Hydreigon can run, he's quite easy to fit on a team, since he can be a great Scarfer, Specs user, and even a great Sub Rooster like Kyurem. However, nothing compares to his mixed sets, which scares the shit out of any team that crosses it. Since his move pool is huge, he can easily adjust to your team's weaknesses. If your team has a huge problem against bulky Psychic and Ghost types, then Dark Pulse is a great STAB to threaten Reuniclus and Jellicent. If your team hates Sub CM Rain Rachi, then EQ can prevent it from setting up on you and is a better move to nab the OHKO on Max HP Heatran. If your team doesn't really seem to have any specific problems, then Roost can be used to improve it's longevity and to compensate for the LO recoil. If put in the hands of the right player, Hydreigon is easily:
"A Rank: Reserved for Pokemon who can sweep or wall significant portions of the metagame, but require some support or have some flaws that prevents them from doing this consistently. Supporting Pokemon in this rank may give opponents free turns or cannot create free turns easily themselves, but can still do their job most of the time.
Also, he looks like a badass. That alone should give him an A-Rank :D.