Alright so if this thing was allowed in OU, and I highly doubt it will be, it would be the most badass wallbreaker in the tier.
Let's take Black Kyurem and assume he has the attacking stats of 160 physical attack and 120 special attack. Now with a Life Orb equipped in a Naughty nature equipped let's see what we can do. Note I am not using any of there Electric moves since we don't know what they are going to get. I am just using the "givens" for moves. If we added stuff like wild charge into the mix (which zekrom gets) many of these calcs would be quite different (Heatran in paticular).
"Given" moves used: Outrage, Hidden Power Fire, and Ice Beam
Ice Beam no investment vs Physically Defensive Skarmory: (62%-73%) Guaranteed 2HKO.
Ice Beam no investment vs Specially Defensive Skarmory: (43%-50%) It has a 48% Chance to 2HKO after SR. But what is Skarm going to do back phaze? Can get killed by anything that comes in and will die to SR if it switches out.
Specially Defensive Heatran vs full investment Outrage
Outrage: 155-183 (40.25 - 47.53%) -- 5.08% chance to 2HKO after Stealth Rock
Outrage: 155-183 (40.25 - 47.53%) -- 98.44% chance to 2HKO after Stealth Rock and Spikes
Specially Defensive Jirachi vs Full Investment Outrage
Outrage: 163-192 (40.34 - 47.52%) -- guaranteed 3HKO after Stealth Rock.
Outrage: 163-192 (40.34 - 47.52%) -- 60.55% chance to 2HKO after Stealth Rock and Spikes
Standard Brongzong vs Full Investment Outrage
Outrage: 134-158 (39.64 - 46.74%) -- guaranteed 3HKO after Stealth Rock
Now what about the things that aren't Steel types but can stand up to Outrages? The Big three being Hippowdon, Tangrowth, and Slowbro Hippo and Tangrowth are OHKO'ed by Ice Beam. What about Slowbro?
Defensive Slowbro vs Full investment Outrage: 220-261 (55.83 - 66.24%) -- guaranteed 2HKO
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Specs White Kyurem (base 160 sp. atk max+ sp.atk)? Borked
Draco Meteor vs Specially Defensive Heatran: 173-204 (44.93 - 52.98%)
Draco Meteor vs Specially Defensive Ttar (Careful 252 Sp. Def EV's)
Draco Meteor: 316-373 (78.21 - 92.32%) -- 37.5% chance to OHKO after Stealth Rock
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Basically with SR and 1 layer of Spikes Black Kyurem can 2HKO the entire metagame. The crazy thing is that this is only with the given moves Outrage, Hidden Power, and Ice Beam. We don't know what other physical Electric moves Kyurem will even get. So yeah I think it is pretty safe to say the both Kyurems will be Uber. Please don't get started on quick bans I want to use them so badly :*******(