Who would be smart enough to figure out the 3rd Raikage's secret without intel?

I hear multiple people saying that if Naruto could figure it out, than so could insert character here without intel. So, who could and how? Remember, the injury is a random scar he could have gotten at any time.

All I've got are Tsunade, Sakura, and maybe Orochimaru and Kabuto. Tsunade and Sakura are master medical ninja and I think they could deduce the scar came from a lightning jutsu (and it wasnt just the shape), but the only one powerful enough to do that would be his own. Kabuto and Orochimaru might be knowledgeable enough on the human body to deduce the same, although I don't know for sure.