Vincent Valentine is a former member of the a central intelligence
agency called the Turks--it is not exactly known why he left. He has
quite a history with Shinra, the "mother" organization of the Turks.
During his tenure with the Turks, he fell in love with a woman named
Lucrecia--however, it was not meant to be. Lucrecia disappeared off
of the face of the planet, and Vincent himself was betrayed by the
Turks. They shot him, and set him up for some experiments lead by
the lead genetic scientist of Shinra, Professor Hojo. Hojo really
screwed up Vincent's genetics, turning Vincent into a bit of a freak
of nature.
Vincent spent ten years sleeping deep underground a mansion in the town
of Nibelheim, until he was disturbed by a soldier named Cloud. After
some discussion about Shinra, Vincent joined Cloud and his comrades.
For a long time, that was it. Vincent assisted Cloud in his endeavours,
and he later found Lucrecia, the woman he had fallen in love with so
long ago. He found out that she too had been wronged by Hojo in much
the same way as he had been; however, he found this out after
she was already gone. Vowing revenge on Hojo, Vincent continued his
travels with Cloud. During an invasion on Hojo's headquarters at a
city called Midgar, Vincent met up with Hojo, who had even used his
genetic experiments on himself in order to gain strength. Regardless
of Hojo's extra strength, Vincent came out on top, only partially
avenging the wrongs committed towards him and his love. However, he
still remains in his freakish state...