Doppelganger is a villain who is similar to Spider-Man. He has six arms and could in some way swing "webs" and climb walls.
Doppelganger was an evil, near-mindless duplicate of Spider-Man that was created by Magus during the battle known as the Infinity War.
The six-armed creature was one of many doppelgangers created by Magus during this conflict. The Doppelganger possesses Spider-Man's strength, speed, wall-climbing abilities, and spider-sense, and also has six arms, claws, fangs, and the ability to produce its own razor-edged webbing.
Although the Doppelganger was killed during the Infinity War by the Hobgoblin, he was mystically revived by the Demogoblin. When Magus was defeated by Adam Warlock at the conclusion of the Infinity War, all of the doppelgangers were destroyed except for the Spider-Doppelganger, thanks to Demogoblin's magic forming a psychic link between the Doppelganger and the Demogoblin. For a time, he was a 'pet' to Demogoblin, but the two went their separate ways after a fight.
Doppelganger later joined up with Carnage, Shriek, Carrion, and Demogoblin during the infamous "Maximum Carnage" killing spree. In the process, Shriek became a sort of adopted mother to Doppelganger, making him even more dangerous as he followed Shriek's instructions in battle with Spider-Man. Later, when Carnage turned on Shriek, Doppelganger intervened and Carnage stabbed the Doppelganger and threw him off of a skyscraper.
Doppelganger reappeared and attacked an armored car in an attempt to bust out Shriek. Before Spider-Man and Iron Man could intervene, he was defeated and cut in a half when shot by Royal Blue. At Hall Industries, he revives and escapes with Shriek to find Cletus Kasady. After Kasady returned as Carnage, he and Shriek helped him to spread chaos in Manhattan until Iron Man and Spider-Man defeated Carnage with the help of Scorn, Carnage's new spawn. He later escaped with Cletus to Doverton, Colorado.