Vice was built as a replacement for Zero as head of the 0th unit, but his creator snapped and placed the Maverick Virus inside his CPU. The accidential fall into the Cleft awoke that faint spark and drove Vice to become completely Maverick.
He had multiple confrontations with the Hunters, driving Seikou towards falling to the Virus and infecting Variance with a modified strain. This lead to both parties being dismissed by the Hunters.
At some point, he became the Champion of Jango. Soon after, he met Rika and decided to use her growing madness as a tool, manipulating her to kill Seikou. While this failed, he and Rika bonded, and eventually he allowed her to cure the Virus as best she could.
Vice died at Seikou's hands, but his memory and appearance was, with Rika's help, attached to a former Sniper Joe. The "rebuilt" Vice and Rika are now married.
Ah yes, Vice. One of my so-called champions in the Middle Realm.
He faired much better that Fortissmo creature. Vice was half forced into my service, and like the others, thought that he could do as he wished with my power.
My tampering with him seemed to have set off something dormant in him, however.
The 'Mavrick Virus' as the machines term it. He attempted at least once to end his own life because of it, and the fool woman Rika that fell in love with him. If one truely can love a machine.
It was his attempted suicide that delivered Rika into my hands. Ultimately, it was my influence that pushed the two apart, and likely what pushed Vice into his own death.