Since we missed the natures in the original announcement, here are the natures that are accepted by the NPCs.
Best IV Judge
__Good Natures__: "Adamant", "Jolly", "Modest", "Timid", "Calm", "Bold"
__Bad Natures__: "Lax", "Mild", "Gentle", "Lonely", "Rash", "Naughty"
Worst IV Judge
__Good Natures__: "Lax", "Mild", "Gentle", "Lonely", "Rash", "Naughty"
__Bad Natures__: "Adamant", "Jolly", "Modest", "Timid", "Calm", "Bold"