Ninetales @ Firium Z or Life Orb or Grassium Z
Ability: Flash Fire  
EVs: 252 SpA / 4 SpD / 252 Spe  
Timid Nature  
IVs: 0 Atk  
- Nasty Plot  
- Fire Blast  
- Energy Ball  
- Psyshock / Dark Pulse 
Ninetales @ Leftovers  
Ability: Flash Fire  
EVs: 252 SpA / 4 SpD / 252 Spe  
Timid Nature  
IVs: 0 Atk  
- Substitute  
- Nasty Plot  
- Fire Blast  
- Energy Ball  

Additional Moves: Hidden Power [Ground]
Additional Items: Salac Berry, Passho Berry
Notes:
-Life Orb may be used over Firium Z, allowing Ninetales to pick up a guaranteed 2HKO with +2 Fire Blast against Lickilicky, Cradily, and Togetic. Grassium Z provides a strong nuke against Carbink, Poliwrath, and Silvally-Water. 
-Psychock is used to OHKO Muk at +2 after Stealth Rock damage (Life Orb is a guaranteed OHKO), and 2HKO Hakamo-o. Dark Pulse can be used over Psyshock to hit Grumpig for super-effective damage. However, Grumpig tends to carry Colbur Berry so the effectiveness of Dark Pulse is generally inferior compared to Psyshock. Finally, Hidden Power [Ground] is a niche option to hit Fire-types such as Rapidash, Torkoal, and it also hits Probopass for 4x super-effective damage. 
-Substitute + Nasty Plot gives Ninetales a lot of room to set up freely. For example, with Substitute, Ninetales has the ability to beat Pyukumuku 1v1 and avoid status moves. 
-A Salac Berry and 4 HP EVs turn Ninetales into a strong late-game sweeper. Choice Scarf users faster than +1 Base 100 Speed are uncommon which makes Salac Berry Ninetales difficult to outspeed. However, Ninetales becomes very susceptible to priority moves if its Substitute is broken. 
-A Passho Berry allows Ninetales to more easily take on Water-types such as Basculin and Simipour while it attempts to sweep.