Beast Boost
Raises this Pokémon's highest stat by one stage when it faints another Pokémon.
In game description
The Pokémon boosts its most proficient stat each time it knocks out a Pokémon.
Pokemon with Beast Boost
Using Beast Boost in Cobblemon
Abilities are passive and always active, so Beast Boost 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.