Nidaime Hokage (which means the Second Hokage in English) of the Hidden Leaf Village, named Senju Tobirama, was Hashirama's (the First Hokage) younger brother and the granduncle of Tsunade. Not much is known about him, and we've only seen him in battle when he was summoned by Orochimaru together with Shodaime to fight against Sandaime. He can perform jutsus in an instant and he specializes in water-based jutsu. We saw him use high level water jutsus in an area where there was no natural source of water, he was able to summon an extremely large amount of water in seconds, quickly flooding an area. His great skill and strength shows us he was truly a very powerful Hokage.