Hey guys,

I will have to go with Itachi. As far as my anime knowledge goes, they always have a new enemy kill off the old enemy. Meaning, back before ep. 80, we thought Oro was the strongest. Now, we know Itachi is the strongest and Oro is past his prime. So, in order for viewers to see the power of the evil (so that when Naruto kicks his ass it will b cooler), he kills off Oro in one blow.