Mega Rayquaza
180 base attack + band using Dragons Ascent/Outrage will slaughter any non resistant types
252+ Atk Choice Band Mega Rayquaza Outrage vs. 248 HP / 216+ Def Rotom-W: 292-345 (96.3 - 113.8%) -- 81.3% chance to OHKO
(292, 295, 300, 303, 306, 310, 313, 316, 319, 324, 327, 330, 334, 337, 340, 345)
Murders one of the most common tanks in the game
Rampardos
165 Base + Band Head Smash. even resisted will still probably OHKO
252+ Atk Choice Band Mold Breaker Rampardos Head Smash vs. 248 HP / 216+ Def Rotom-W: 340-402 (112.2 - 132.6%) -- guaranteed OHKO
(340, 345, 349, 352, 357, 361, 364, 369, 373, 376, 381, 385, 388, 393, 397, 402)
Decimates It with no chance of survival