My counter is.....
Azumarill Skarmory!
Skarmory @ Leftovers
Trait: Sturdy
EVs: 252 HP / 252 Def / 4 Atk
Impish Nature (+Def, -SpA)
-Whirlwind
-Spikes
-Brave Bird
-Roost
Meet Skarmory,a bane to all Dragons lacking a fire move(other than the Latis of course).It takes a pittance from Choice Banded moves,and the only way Haxorus can 2HKO it without boosts is by using Specs HP fire (lol).I don't really understand the smogon EV spread,so I will be using this one instead.The only reason I recommended Skarmory is because it cannot be KOed without.boosts or isn't set-up fodder for Haxorus without Taunt,like Ferrothorn and Forretress respectively.Every other steel type in the tier is OHKOed with a +2 Superpower,incuding Jirachi,Scizor,and Bronzong.Stuff like Landorus-T,Hippowdon,and Gliscor are all destroyed by a +2 Aqua Tail (though Hippowdon can tank one +2 Aqua Tail).
The problem is,despite massive bulk,Haxorus can still burst through it,as a +2 Rain-Boosted Water Gem-boosted Aqua Tail has a 50% chance of KOing it without Stealth Rock.I know almost no one runs that,but even the most recommended set on smogon can OHKO Skarmory with a Fighting Gem-boosted +2 Superpower 62.5% of the time.
Haxorus is a dragon-type,and many OU pokemon deemed uncounterable (i.e.Hydreigon and Kyub) are dragon types.This because so few things actually resist Dragon,and Dragon types have the power to burst through bulky non-resists (i.e.Hippo,Gliscor,Lando-t,Tangrowth,Slowbro) or the coverage to burst through almost all it's resists,dragon types are nigh-uncounterable.As shown above,Haxorus can still go through Skarmory,and therefore,Skarm isn't really a "counter",its just a really strong check,and in my opinion,the strongest check there is.There is no counter to Swords Dance Haxorus,as it can OHKO or 2HKO every pokemon in existance (even Shedinja due to Mold Beaker) at +2 with the correct move from the Superpower set.
Other sets like the DD set and Choice Scarf sets are easier to handle,as previously mentioned steels like Scizor and Bronzong will have an easier time defeating it.Skarm will now be a perfect counter,besides the rare Taunt.
The best way to handle this thing is by revenge killing,which means Haxorus will give no problems to HO.It's speed is lackluster,which means almost every offensive threat in OU is a threat to Haxorus.While Scizor cannot OHKO Haxorus like many other revenge killers,it is the best defensive revenge killer to Haxorus.Other Dragons are fine checks to Haxorus,the only exceptions are Kyurem-B(which it outspeeds) and Dragonite(which is OHKOed through Multiscale).
Well,thats my take on handing Haxorus.
