The Shredder
Two members of the Foot Clan, Oruku Nagi and Hamato Yoshi competed for the love of a woman. The woman was named Tang Shen. She loved Hamato Yoshi instead of Oruku Nagi.
Oruku Nagi, was enraged. He attacked Tang Shen. Hamato Yoshi attacked and killed Oruku Nagi. Hamato Yoshi, felt shocked for killing a member of the Foot Clan. Hamato Yoshi, his pet ret, Splinter and Tang Shen left Japan to live in America. Oruku Saki, younger brother of Oruku Nagi found about his brother's fate. Oruku Saki tracked down Hamato Yoshi and Tang Shen. He murdered the couple.
Oruku Saki joined the Foot Clan, like his brother. He was trained to a Ninja. Oruku Saki rose through the ranks of the Foot Clan. He became in charge of the American branch of the Foot Clan. The clan, under Saki's leadership, did criminal activities, such as assassination. Oruku Saki, and the Foot Clan relocated to New York. Splinter, Hamato Yoshi's rat mutated. Splinter could speak and trained four Ninja Turtles, who were mutated as well.
Fifteeen years later, Oruku Saki ran a security company. Splinter felt the Turtles were ready to challenge him. Oruku Saki became the Shredder. http://www.youtube.com/watch?v=lKEIfBBbgm8 That day, The Shredder became the Teenage Mutant Ninjas Turtles' arch-nemesis.
Originally he was supposed to only appear in one issue of the comic, but his popularity saw him return; Peter Laird had said that it was not his and Kevin Eastman's intent for him to become the "Darth Vader" of the TMNT universe, but he had indeed become the chief villain.
The End