Senju Clan the Strongest Clan

Gottheim
Chapter 399; p.01
Madara: The first man ever to take the name of Hokage./The clan Hashirama led, the Senju...//was acknowledged by every shinobi clan without exception for its superiority. And feared, more than anything else.

Chapter 386; p.10
Itachi: Madara used his power to subjugate every clan one after another./Then he joined hands with the clan that was hailed as the strongest, the Senju of the Forest, thus establishing a new organization.