Kraven the Hunter

Kraven received his powers in a tragic case of misfortune. Whilst in Africa, Kraven's fiancé Dr. Mariah Crawford was attacked by a hoard of lions. The fight with the lions left Sergei critically wounded, Dr. Crawford used a wonder drug in hopes to heal his wounds. She was warned not to, as the drug, in its current condition was dangerous, but she felt she had no choice.

Kraven's physical recovery was astounding, but his mind was in a state of despair. He began hunting vigorously and now called himself Kraven The Hunter, forcing Dr. Crawford to search for a cure. Fleeing to America, she continued her research until Kraven followed her. She eventually concocted one after Spider-Man tangled with the Hunter.

The tables were turned many months later. With Spider-Man now Man-Spider, Dr. Crawford pleaded for Sergei to return to hunt Spider-Man down so he couldn't hurt anyone whilst she continued to perfect her cure for his condition. With some help from The Punisher, they managed to cure Spider-Man.

Disaster struck again after Dr. Crawford became seriously ill from the plague. Fearing for her safety, Kraven gave her the same serum, which tuned him into Kraven to heal her. When she changed into Calypso, he again took the serum to hunt her down before she hurt anyone. After Debra Whitman managed to restore her sanity, Kraven and Calypso fled together.