Naruto was the one whose spirit was able to summon the So6P, enabling both Naruto and Sasuke to get their current power. Both of them are necessary to defeat Madara.
I've always embraced tolerance, but I can't embrace tolerance for groups whose belief systems include hatred and discrimination. I guess that makes me intolerant, too.
Parents dead. Idolizes sensei (Hiruzen) and was reputed to be exceptional. Gets hurt and angry when Hiruzen passes him up in favor of Minato. This story proves there's nothing more dangerous than a butthurt genius.
It never made sense how the sage left a tablet that could only be deciphered by the elder son. I always suspected the elder son tampered with the tablet or actually made it himself.