Scarlet Spider

Scarlet Spider was the first spider-person before Spider-Man.

Ultimate Spider-Man
According to himself, Kaine was captured by Doctor Octopus and was subjected to many painful experiments by him. He was able to escape and forced to live in the sewers. Since then, Scarlet Spider held a personal vendetta against Dr. Octopus for what he did to him.

Trivia

 * This is Kaine's first animated appearance.
 * Unlike most of his incarnations, who are actually clones, Kaine is a human mutated with spider powers.
 * Like his Ultimate comic book counterpart, Kaine's existense as a spider people was created by Doctor Octopus.
 * Kaine is the first spider people before Peter Parker/Spider-Man.
 * Kaine is also the first Scarlet Spider before his alter ego was temporarily used by Flash Thompson (shortly before turning into Agent Venom).