Keldeo-Resolute @ Agony Boots / Distress Glass  
Ability: Knight's Blade  
EVs: 252 SpA / 4 SpD / 252 Spe  
Timid Nature  
IVs: 0 Atk  
- Hydro Pump  
- Secret Sword  
- Scald  
- Hidden Power [Ice]

Keldeo @ Waterium Z
Ability: Knight's Blade
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
- Calm Mind
- Hydro Pump
- Secret Sword
- Taunt

Keldeo's new ability in Knight's Blade boosts the already absurd power of Secret Power to extreme levels, making it an even more threatening Special Attacker to special walls, especially with the prevalence of Chansey. The Torment items also give Keldeo and better speed tier or let hit near-Specs power without being locked into a move.
Other Options: Choice items, Icy Wind > Hidden Power [Ice], Stone Edge