Intimidate

Lowers opponents' Attack one stage upon entering battle.

Full effect

When this Pokémon enters battle, the opponent's Attack is lowered by one stage. In a double battle, both opponents are affected. This ability also takes effect when acquired during a battle, but will not take effect again if lost and reobtained without leaving battle. This ability has no effect on an opponent that has a Substitute. Overworld: If the first Pokémon in the party has this ability, any random encounter with a Pokémon five or more levels lower than it has a 50% chance of being skipped.

In game description

When the Pokémon enters a battle, it intimidates opposing Pokémon and makes them cower, lowering their Attack stats.

Pokemon with Intimidate

Using Intimidate in Cobblemon

Abilities are passive and always active, so Intimidate 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.