Opportunist
Copies stat boosts by the opponent.
Full effect
If an opponent’s stat is boosted, the Pokémon seizes the opportunity to boost the same stat for itself.
In game description
If an opponent's stat is boosted, the Pokémon seizes the opportunity to boost the same stat for itself.
Pokemon with Opportunist
Using Opportunist in Cobblemon
Abilities are passive and always active, so Opportunist 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.