The best combo at any point of the game would have to be
Noivern @ life orb
Evs: spa:252 spe:252 hp:4
Nature: Timid
Ability: Telepathy
-boomburst
-draco meteor
-dragon pulse
-air slash
Exploud Choice specs
Ev: hp:252 spa:252 def:4
Nature: modest
Ability: soundproof
-Boom burst
-surf
-flamethrower
-thunder bolt
Dual boombursts with explouds hitting much harder. You can also use choice scarf to up his speed but, there powers alone just wrecks. And is definatly my favorite combo to do this gen
I've found that tailwind on noivern works well, also I'm somewhat hesitant to run choice specs on exploud without better coverage on noivern. Interestingly enough, noivern can learn flamethrower to mess with the steel and steel/fairy types that wall this combo. Noivern also gets focus blast, psychic, shadow ball and dark pulse, but there's not really a place to put them. Also the only rock type you're going to run into often is tyranitar and maybe carbink.
I'd say
Noivern @ yache berry
Evs: spa:252 spe:252 hp:4
Nature: Timid
Ability: Telepathy
-boomburst
-tailwind
-dragon pulse
-air slash
Exploud @ Metronome
Ev: hp:252 spa:252 def:4
Nature: modest
Ability: soundproof
-Boom burst
-surf
-flamethrower
-thunder bolt
this set lets exploud take care of coverage, while still allowing it to get off some nice boombursts if it wants to, and the tailwind lets exploud outspeed anything with less than 172 speed