>>30493230This. Even if you have to breed for a while longer than you'd like for those last 2-3 Abra, it's easier to breed than to encounter something, hope it's an Abra, hope it's a Synchronize Abra, and hope it's a Synchronize Abra with the Nature you want.
Besides, you're gonna use maybe 6 of those Natures? Definitely not the Neutrals, so that's already 5 out of the way. You're not gonna use a defense/sp defense down Nature because you like living, so that's another 10 natures you won't use except to go for a Mixed Attacker. Speed down is also a no-go unless you're gonna run a Trick Room comp. That leaves
>+Attack; -Sp. Atk>+Sp Atk; -Atk>+Speed; -Sp. Atk>+Speed; -AtkI don't really play competitive, so I could be wrong, but that's my understanding of Natures.