If you want to break Kyurem-W using a viable strategy, use Future Sight Calyrex-S. It breaks down Eternatus easily and also brings Kyurem-W to the range for Water Spout to 2HKO it.
Calyrex-Shadow @ Focus Sash
Ability: As One (Spectrier)
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
IVs: 0 Atk
- Future Sight
- Nasty Plot
- Baton Pass
- Astral Barrage
How to use: set-up Future Sight, lure Yveltal, switch out with Baton Pass, bring in Kyogre, Water Spout and watch it 2HKO Eternatus/Kyurem-W.
252 SpA Calyrex-Shadow Future Sight vs. 0 HP / 216 SpD Kyurem-White: 192-226 (49.1 - 57.8%) -- 96.1% chance to 2HKO
252 SpA Kyogre Water Spout (150 BP) vs. 0 HP / 216 SpD Kyurem-White: 111-131 (28.3 - 33.5%) -- Guaranteed 2HKO at 51% of HP which is the minimum roll.
Also AG2CL2 is up, but there's this stupid Palkia not something like Kyurem-W which is infinitely better :(
https://www.smogon.com/forums/threads/ag-core-ladder-challenge-season-2-cycle-2-post-183.3673427/post-8869464