What does the Lonely nature do?

Lonely raises Attack by 10% and lowers Defense by 10%.

What stat does Lonely increase?

Lonely increases Attack by 10% and decreases Defense by 10%. HP is unaffected.

A Lonely Pokémon likes Spicy flavors (tied to Attack) and dislikes Sour flavors (tied to Defense).

Yes. Use a Lonely Mint to apply the Lonely stat effect to any Pokémon without changing its displayed nature.

Nature

Raises Attack, lowers Defense.

Raises Attack +10%

Lowers Defense −10%

LikesSpicy

DislikesSour

Physical attackers that don't need to take physical hits.

Brave −Speed Adamant −Sp. Atk Naughty −Sp. Def

What does the Lonely nature do?: Lonely raises Attack by 10% and lowers Defense by 10%.
What stat does Lonely increase?: Lonely increases Attack by 10% and decreases Defense by 10%. HP is unaffected.
What flavor does a Lonely Pokémon like?: A Lonely Pokémon likes Spicy flavors (tied to Attack) and dislikes Sour flavors (tied to Defense).
Can I change a Pokémon to Lonely?: Yes. Use a Lonely Mint to apply the Lonely stat effect to any Pokémon without changing its displayed nature.