Russell "Russ" Gregory (2012 TV series)

History
Jake is a bounty hunter and an alien exterminator. According to him when he was telling his tales to the Turtles, he lost his eye while fighting a crocodile with his bare hands when he was 8 years old. Years later he married a beautiful naturalist named Kaya. One day when he was hedding home, after collecting some bounties, he found a strange canister of ooze and brought it home to show Kaya what he had found.

Then their cabin was under attack by Kraang droids, who were after the canister of ooze, and they were taken by the Kraang droids to their lair where Jake watches in horror as the Kraang experimented on Kaya.

When the Kraang were about to experiment on Jake he made his escape, during the escape he made his way through a pen of kangaroos, and slipped into a tank of ooze and became a mutant kangaroo. He used his new kangaroo abilities to escape the oncoming Kraang droids.

After his escape he vowed to avenge his wife by becoming an alien exterminator and made his new home in an aboriginal tribe.

Years later he is hired by the Shredder to assassinate some aliens (the Turtles)