Why can Buzzwole ex use Big Beat on consecutive turns?
When Buzzwole ex uses Big Beat, the attack applies an effect on Buzzwole ex that prevents it from using Big Beat during the next turn. However, all effects applied to a Pokémon are removed when that Pokémon returns to the Bench. Because of this, if Buzzwole ex returns to the Bench after using Big Beat, the effect from Big Beat that prevents it from being used on the next turn is removed, and Buzzwole ex can use the attack again on the next turn.