Kaine is a Marvel Comics supervillain. He is one of the first "failed" clones of Peter Parker (Spider-Man), created by Professor Miles Warren, the Jackal. The character first appeared in Web of Spider-Man #119, and was created by Terry Kavanagh and Steven Butler.
The Jackal went on to create a new, better clone; the man who would become Ben Reilly. When the Jackal used Reilly against Peter, the ensuing battle left Reilly and the Jackal for dead. They both managed to survive; the Jackal placed himself into suspended animation in a cloning pod to awaken later; and Reilly left for New York.
Behind the scenes, Norman Osborn managed to have the files on Ben and Peter switched, so the Jackal would think Peter was the clone and Ben was the real deal. Consulting the Jackal's files, Kaine also believed the same, so he followed Ben Reilly through his "exile". For a time, he found love in the arms of police detective Louise Kennedy of Salt Lake City, but when she was discovered to be working for the criminals, coupled with Kaine's increased cellular degeneration pushing him even further towards insanity, Kaine finally lost it. After killing Louise (Although a part of him still loved her), Kaine continued to stalk Ben, making it appear as though Janine Godbe, the woman Ben loved had committed suicide and then framing Ben for murder by committing a number of murders in which Ben would be blamed (Kaine and Ben had the same fingerprints), hoping to give who he thought was the clone (Peter) the life he could never have.
Peter wanted Kaine to stand for what he had done, but Kaine initially refused. The two fought and ended up getting dragged into a mock-trial where Spider-Man was on trial, Kaine was his defense attorney, Carnage was the prosecutor, several Ravencroft inmates were the jury and a powerful being known as Judas Traveller was the judge. During the one-sided trial, Kaine tried to physically fight off all those who were against Spider-Man before Traveller returned them to their previous place of battle.
After an incident involving a superpowered villainess named Stunner, a weakened Kaine still refused to confess to his crimes. Spider-Man responded by knocking Kaine out and webbing him up before heading to the courthouse. Kaine reawakened before they arrived and struggled again with Spider-Man in refusing to confess. At this point, Kaine admitted that he'd done everything to protect Peter's life and revealed that he was the first clone of Peter, now partially degenerated. Spider-Man decided that if Kaine wouldn't reveal the truth, then he would reveal his true identity to the entire courtroom and end everything. Kaine pleaded for Peter not to do this and eventually gave into revealing the real truth about the murders and the "Mark of Kaine".
The Jackal, curiously, then placed Kaine in a regeneration pod. When the pod was next seen, it was empty.
One of the Game's main sponsors, James Johnsmeyer, found the pod containing the revived Kaine, and decided to initiate him into the competition, sending the Rhino to fight him. After Kaine's refusal and escape, thanks to temporary partner Shannon, Johnsmeyer still attempted to involve Kaine by allowing other Game competitors to attack him (Joystick and Polestar).
Spider-Man interfered in the skirmish and got sidetracked by Joystick and Polestar while Kaine put a near-fatal beating on Rhino and escaped with Shannon. Before they were able to get away, Spider-Man had managed to tag Shannon with a tracer and he pursued them once Polestar and Rhino were taken into custody. He found them moments before the police, but after an incident that threatened to kill the officers, Kaine and Shannon escaped again.
This time, Kaine's destination was Johnsmeyer's headquarters. Spider-Man found them once again after Kaine managed to single-handedly destroy all of Johnsmeyer's rooftop security defenses, but once inside, Johnsmeyer revealed that Shannon--who was still working for Johnsmeyer during the entire ordeal--had been manipulating and deceiving Kaine. Kaine, not wanting to become a puppet of anyone ever again, tried to kill Shannon but was persuaded by Spider-Man not to do so. Kaine left, vowing to take down every sponsor of the Great Game.
Several months later, however, he was shown escaping from jail alongside many other super-powered criminals in an issue of Thunderbolts. It has never been outright stated what caused this change of character, although it is most likely that the writer or artist for Thunderbolts simply decided to add Kaine into the jailbreak scene because he didn't realize that Kaine had willingly let himself be arrested.
Later stories subtly implied that Kaine broke out to try and stop Norman Osborn after finding out that Osborn was still alive and had masterminded the Clone Saga, as a few issues of Spider-Man briefly showed Kaine working against Osborn's agents in southern Europe.
The last mention of Kaine was an offhand line from one of Osborn's men saying that Kaine had been "dealt with", although what he meant by that was left ambiguous. Nonetheless, Kaine has not been seen or heard from since.
Kaine attempted to kill the Kingpin but was stopped by Spider-Girl, the daughter of Peter Parker, and sent to prison. There, he was recruited by Special Agent Arthur Whedon as part of a team of captured supervillains given the opportunity to redeem themselves by working for the government. He appears to be genuinely interested in reformation, and has since been supportive of Spider-Girl and acted as an advisor to her.
If either Spider-Girl or Darkdevil is aware of their semi-genetic relationship to Kaine, it has not been revealed.
Spider-Man villains | MC2 | Doppelgängers | Fictional Americans in Marvel Comics | Fictional clones | Fictional New Yorkers | Fictional precognitive characters