Part 1: Black

Black Kyurem has that monster attack stat and some moves to use. Terravolt is a nice ability too. However, it has a movepool that is just crying for more. Being an ice type in ubers is a death sentence as well.

The only Black Kyurem you will probably ever see
Nature: Adamant/Jolly
EVs: 252 attack and speed, 4 hp
@: Choice Band/Choice Scarf

Outrage
Fusion Bolt
Dragon Claw
Freeze Shock

One advantage that Black Kyurem has is that it can counter Kyogre very well, thanks to a resistance to water and electric and doesn't fear Ice Beam.

Part 2: White

White Kyurem is scary. Turboblaze is an ability that is welcomed, as well as a nice movepool. Type could be better.

Whiteout
Nature: Modest
EVs: 252 sp attack and speed, 4 hp
@: Choice Specs

Draco Meteor
Ice Beam/Dragon Pulse
Fusion Flare
Earth Power

Unresisted by all.