Is it Itachi? But it seems like Itachi is being used as a foot soldier, running missions for his boss. So are there ninjas in Akatsuki that are stronger than Itachi?
On the other hand, in the anime (and maybe the manga, I forget), Itachi states that trying to kill Jiraiya would only end in both sides dying in the best case, and that bringing MORE men would not matter. So does that mean that even if Itachi asked his boss to help, it would not matter? That might mean Itachi is stronger than anyone in his organization.