Fang I was a Captain America villain. Fang III an opponent of Morbius.
Fang II was consumed by a Brood embryo in Uncanny X-Men #162, and ceased to exist as himself. His death as a Brood has not been depicted, but he more than likely died in #167 with the destruction of Broodworld. Multiple versions of Fang have appeared since then with the Imperial Guard, as new Subguardians of the Fang-type may have been promoted (and died). However, Wolverines #8 established that the original Fang is alive, and Lupaks regenerate so long as their remote invisible organ isn't destroyed. So, any appearance since Fang's first return in Starjammers (1st series) #4 is ambiguous whether it's the original or a replacement.