The Pokémon shows moxie, and that boosts the Attack stat after knocking out any Pokémon.
This Pokémon's Attack rises one stage upon knocking out another Pokémon, even a friendly Pokémon.
This ability does not take effect when the Pokémon indirectly causes another Pokémon to faint, e.g. through poison or Spikes.
If this Pokémon uses a contact move to knock out a Pokémon with Mummy, the former's ability will change without taking effect.