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LO Moonblast Energy Ball Encore Whimsicott is able to:
Outspeed and OHKO
100% Diancie-Mega, Hydreigon, Scrafty
75% Keldeo (dies to own LO), Terrakion (dies if LO), Flame Orb Conkeldurr
18.8% Latios
12.5% Azumarill
80.2 - 95.7% Rotom-W
76 - 90.6% Hoopa-Unbound
70.2 - 80% Bisharp
67.8 - 80.1%...
Trick Room, being incredibly common in UU (a lot more than in OU), every team needs at least one check to it.
http://replay.pokemonshowdown.com/luster-doublesalmostanyability-228