Run this with some pokemon that can kill steels, ghosts and rocks for you.
Meloetta @ Choice Scarf
Timid / Modest
252 Sp.Atk / 252 Spd / 4 something
- Echoed Voice
- Psychic
- Thunderbolt
- U-turn
For those of you that don't know the beauty of Echoed Voice, it starts out at 40 power then gains 40 every turn up to 200. Its really easy to come in and revenge something low on HP, hit the next pokemon with an 80 power STAB move, live a hit, then proceed to murder the rest of the opponent's pokemon. Its a really good, unknown-to-most move.
This kind of set can also work with Togekiss.