Something I just noticed about Kyurem: If his forms' HP stats are changed, the base form's will have to be too. Also, it doesn't really make sense for Kyurem to have a higher BST than Kyurem-B and Kyurem-W. My suggestions:
HP 125 -> 95
Atk 130 -> 120
Def 90 -> 90
SpA 130 -> 120
SpD 90 -> 90
Spe 95 -> 85
BST 660 -> 600
Ability: Mold Breaker / Snow Warning (HA)
Glaciate: 85 BP, 95 Acc, Lowers the foe's Speed by 1 stage
I think this would be good for making it strong in spite of the stat nerf, while not being overpowered.
I was trying to think of something for standard Kyurem, just couldnt come up with anything, so this helps a lot! Thanks!