Unnerve

Prevents opposing Pokémon from eating held Berries.

Full effect

Opposing Pokémon cannot eat held Berries while this Pokémon is in battle. Affected Pokémon can still use Bug Bite or Pluck to eat a target's Berry.

In game description

Unnerves opposing Pokémon and makes them unable to eat Berries.

Pokemon with Unnerve

Using Unnerve in Cobblemon

Abilities are passive and always active, so Unnerve costs you nothing to run. If it is marked hidden on a species above, expect it to be harder to obtain: servers differ in whether hidden abilities come from breeding, an Ability Patch, or events.

See the Pokedex for which abilities each species can have, and IVs, EVs and breeding for how to actually pass one down.