Kashii is one of the two giants that guarded the front gate of Enies Lobby.
As a giant, Kashii is not only many times bigger then a normal human, but also equally many times stronger. As proven against the Kairiki Destroyers of the Franky Family, a mere human, no matter what the strength or size, will have no easy battle against them. Kashii and his partner Oimo are natural born fighters. In the end i takes the efforts of the Galley-La's and Franky Family's best fighters, along with the help of Sodom and Gommorah, to down both Oimo and his partner.

Source: http://onepiece.wikia.com/wiki/Kashii