"Despite having devoured the five continents and slurping the three oceans dry, the sky alone remains out of reach for this body of mine that lacks wings, hands, and feet. I am the World Serpent. I am Jormungand." (Also Fenrir and/or Hel depending on my ability, HP, and base form)
Loki's Dragon Child
Ability: Power Construct
Item: Life Orb/Leftovers
Nature: Jolly (+Speed -SpAtt)
EVs: (HP 4) (Attack 252) (Speed 252)
Moves:
Dragon Dance/Coil
Thousand Arrows/Earthquake
Scale Shot/Outrage
Iron Tail
Set Details:
A boosting sweeper set. Dragon Dance jacks up attack and speed, but Coil makes it tank better by boosting defense along with speed with an added accuracy boost to make Iron Tail hit 100% of the time for Fairy and Ice coverage. Zygarde's STABs have near perfect coverage otherwise and are up to preference. Earthquake is a staple Ground power move, but Thousand Arrows can hit and knock down Flying types and Levitate users, meaning the likes of Fire/Flying types, K.Zapdos, Aerodactyl, Crobat, Skarmory, Bronzong, etc have some something extra to fear. Scale Shot boosts speed at the cost of defense and sadly does not have the most consistent power, but it doesn't lock you into a single like Outrage does, though that power is tempting...Item goes to Leftovers or Life Orb depending on if you want survivability or power, while EVs are pumped into attack but mostly speed.
It's a shame Zygarde never got its own game back in gen 6 though: