Yveltal #1:
Level: 69
Nature: Docile
IV: Hp, Attack, Defense
Yveltal #2:
Level: 50
Nature: Impish
IV: Hp, Defense, Sp. Defense
Yveltal #3:
Level: 50
Nature: Jolly
IV: Hp, Sp. Defense, Speed
Yveltal #4:
Level: 51
Nature: Hasty
IV: Attack, Defense, Sp. Attack, Sp. Def.
I'm also considering the...