Pain's biggest/only weakness
I was thinking about this as I saw Pain's scuffle with Kakashi. Pain's strength is his biggest weakness, the fact that his mind is divided up between 6 bodies. In a one-on-one fight, this is a huge asset, since he can focus all 6 bodies on one target. The example being the fight against Jiraiya, where Jiraiya was pretty much overwhelmed by the 6 bodies. The battle going on in the Leaf Village is a completely different type of fight though. Each of the bodies are separated from each other, meaning their individual strengths can't be used to support each other's weaknesses. It also means that Pain has to fight 6 different fights at once, giving each of the bodies his full attention, since none of the Leaf jounin should be scoffed at. I'm curious to see if he's going to be able to split his focus like that and still be as effective as he was during his battle with Jiraiya.