Vincent Volaju

Main antagonist of the movie, Vincent is a rather melancholic introvert.

He was used as a test subject during the experimentation after the Titan War. He was the only survivor in a field of test subjects, ergo, the vaccine only he carried was successful. He was abandoned to die on Titan by the government, but somehow survived and returned to civilization. He has also loved Electra very deeply, but has suffered amnesia from his ordeal and does not remember.

His plan is to release the virus throughout the world, leaving only a handful of survivors. As a side-effect of the virus, Vincent was driven to insanity; which was also aided by the hallucination of golden butterflies he saw continuously (another side-effect of the infection).
Vincent is in many ways a contrast to Spike. Aside from equal physical strength and similar physical appearances, Vincent and Spike are both men who consider themselves to be "dead" due to tragic incidents in their pasts, both kept alive by their love of a woman. The archetypal comparisons between the two have lead many fans to argue that the film itself is merely one of Spike's dreams, in which he confronts the guilt of his past and the end of his own life's situation.

Watanabe has declined to deny or confirm this. It has been stated that he may have been inspired by Bob Dylan and that his look is based on Vincent Gallo.