Hello everyone.. madara"said in the last episode in th anime that he gave pain one of his eyes "rennegan"" will that give us another clue that he is madara or izuna??

well then where did the other rinnegan in pain's eye come from ?

I think when the chakra rods were put into them, they were linked giving nagato control over their jutsu/abilities, and giving them the rinnegan in return. Because he sees/acts through them....well, that's my quess....and to answer the main question, the rinnegan is unlocked because of great suffering and true hate. Maybe Madara tricked/minipulated the two ninja into going into nagato's house. He might have known the ninja would kill Nagato's parent's thinking they were enemies. Ensuring that the troubled desendent of the uzumaki clan, would aquire his rinnegan.....Idk, that's another guess