Gothitelle @ Chesto Berry  
Ability: Competitive  
EVs: 252 HP / 4 Def / 252 Spe
Timid Nature  
IVs: 0 Atk  
- Cosmic Power  
- Toxic / Nasty Plot
- Rest  
- Stored Power

Gothitelle @ Life Orb  
Ability: Competitive  
EVs: 252 SpA / 4 SpD / 252 Spe  
Timid Nature  
IVs: 0 Atk  
- Nasty Plot  
- Psychic  
- Shadow Ball  
- Thunderbolt

Other options: 252 HP / 252 Def / 4 SpD (or creeping Pokemon such as Shedinja and max Speed Machoke)