Kaine was the first Spider-Man clone to be considered a success. Later, it was revealed that the cloning process was flawed, and that Kaine’s cells were deteriorating. This resulted in Kaine becoming deformed and mentally unstable. However, this deterioration bizarrely made Kaine's strength greater and spider-sense significantly surpass Spider-Man's own.

When the Jackal discarded him because of his flaws, Kaine felt rejected, feeling as a son rejected by a father. After he left, he discovered his enhanced powers. He also discovered his “Mark of Kaine,” which left a disfiguration on the victim’s face.

The Jackal created another clone and sent it against Spider-Man, but both were beaten and assumed dead. After the Jackal’s defeat at the hands of Spider-Man, Norman Osborn (Green Goblin) switched Peter and Ben’s files, making it look as if Peter was the clone. Kaine, who broke into the Jackal’s lab to look at these files, was led to believe the same thing, and followed Ben Reilly, aka the Scarlet Spider, as he fled New York.

Kaine fell in love with a Salt Lake City police detective, Louise Kennedy, but Kaine discovered that she was working for criminals. This fact, coupled with his genetic deterioration, drove them apart. He finally went insane and killed Louise. He then stalked Ben. He then made it appear that the girl Ben loved, Janine Godbe, had committed suicide. He then began committing murders, making the police believe that Ben had done it (for they had he same fingerprints) in hopes that Peter (who he thought was the clone) would be able to live the life he was never allowed.

Peter was eventually imprisoned for Kaine’s murders (he too had the same fingerprints) but Ben took his place. Peter attempted to make Kaine take responsibility for his crimes, which led to a fight. In the end, they both appeared at trial with Spider-Man on trial, Kaine as his defense attorney, Carnage as the prosecutor, several Ravencroft inmates as a jury, and Judas Traveller as the judge. Kaine attempted to fight off all those against Spider-Man, and Judas returned them to their previous battle.

Kaine fought with Stunner, and after being severely weakened, he was knocked out by Spider-Man, who tied him up and brought him to the courthouse. Kaine woke before they arrived, and unveiled who he was and that he had done all this for Peter’s sake. Peter threatened to reveal himself as Spider-Man to the courtroom and end everything unless Kaine confessed. Kaine gave in and told everything, including “The Mark of Kaine.”

Peter, after learning that he was supposedly the clone, went to join the Jackal. Kaine refused to let Peter throw his life away and confronted the Jackal, prepared to kill him. The Jackal tricked Kaine into believing that he would be cured of his degeneration, and upon learning the truth, Kaine left, feeling dejected. He went to Mary Jane for answers, and after she taught him about responsibility, he left to help Ben as he fought many Spider-clones. In the ensuing battle, Spidercide impaled Kaine, killing him. Strangely, the Jackal put Kaine into a regeneration pod, and it was next seen empty.

When many of the strongest fighters were pitted against each other in The Great Games, a man named James Johnsmeyer found Kaine’s pod and decided to enter him in the games. Kaine refused, and with the help of a temporary partner, Shannon, he escaped. Johnsmeyer sent Rhino, Joystick, and Polestar to force Kaine into the Games. Ben Reilly in his stint as Spider-Man intervened, and began fighting Polestar and Joystick as Kaine nearly killed the Rhino. Ben stopped him, and Kaine escaped with Shannon. Ben got a tracer on Shannon before they escaped. He found the two just before the police, and Kaine was escaped by threatening one of the officers. This time, Kaine and Shannon went to Johnsmeyer headquarters. Ben found them again, and Kaine destroyed all of Johnsmeyer’s security equipment. Johnsmeyer revealed that Shannon had been working for him all along and had manipulated Kaine the entire time. Kaine attempted to kill Shannon, but Ben convinced him to spare Shannon. Kaine left, vowing that he would take down everyone who supported the games.

Later, Kaine encountered Ben and Janine Godbe who had recently returned to Ben. Kaine saved Ben after initially leaving him to die in a burning restaurant. Kaine finally acknowledging Ben as a brother, instead of an enemy. Kaine turned himself in to the police, and Janine (who was wanted for the murder of her abusive father) followed suit.

Kaine later escaped from prison to fight Norman Osborn, who he learned was alive and had been the mastermind behind the Clone Saga. Later, a soldier for Osborn said that Kaine had been “dealt with,” without elaboration.

Kaine was later listed as an enemy combatant to the Fifty States Initiative.

Powers

Kaine possesses enhanced versions of Spider-Man's abilities. His Strength far exceeds Spider-Man's own. Kaine could fight the Scarlet Spider, Spidercide and Spider-Man to a standstill, with the three each capable of lifting in excess of 10 tons. Kaine's version of the "spider-sense" is so acute that it gives him glimpses into the future. He also possesses an ability to horribly corrode surfaces upon physical contact, which he has used to kill various people.

Alternate Versions

MC2

Kaine is perhaps the only reason that the MC2 universe is any different than the normal Marvel Universe. In this continuity, Kaine rescued a baby May Parker (Spider-Girl in this universe) from Norman Osborn and returned her to her parents.

Kaine became a partner of the Kingpin of Crime, but was betrayed. Daredevil sacrificed his life to save Kaine, and Kaine took him to the regeneration chambers, where he was also trying to help Reilly Tyne. He summoned the demon, Zarathos, to help them, but Zarathos attempted to take Reilly's body. Daredevil fought the demon, and in the end, Reilly became Darkdevil, with the powers of a demon and the heart of a hero.

Kaine later was sent to jail after Spider-girl stopped him from killing the Kingpin. He was offered a position on a new government team for reformed supervillains. He accepted, and had under him Big Man(son of Hank Pym and Wasp), Quickwire( a former Spider-Girl villain), And formerly Raptor and Normie Osborn(Raptor being fully pardoned and Normie losing his powers).

Ultimate Universe

Although he was not named, a disfigured clone wearing a Spider-Man costume kidnapped Mary Jane. Reasoning that Mary Jane can now protect herself when he administer the OZ formula. When she lashed out she became the ultimate version of the Demogoblin. The clone was later killed by Spider-Slayers.