Most of the shinobis in naruto verse which have bad pasts or sufferings in life are really stronger and dominant shinobis.
1.sasuke:his whole clan was destroyed and have to live in pain to kill his own brother
2.naruto:he was an orphan,he dint even saw his parent.he had to live facing those looks from other villagers.
3.neji:he too was an orphan and hated his uncle at his child.
4.kakashi:he needs to face the curse of his father's doings.
5.madara:his family was still unknown but had a brother who was sacrifised in a war.
6.nagato:his parents were too dead in war and lost his best frn.
7.minato:we still dont know abt him,his whole clan were never hrd.his whole clan mite have been swept away(namikaze).