Arachne's powers arose through a government experiment that injected her with a mixture of spider venom and rare plant extracts. The serum gave her abilities similar to those of the Amazing Spider-Man, which she used to launch upon a career fighting crime. Arachne originally appeared in the 1984 comic mini-series "Secret Wars," then going under the name Spider-Woman. She began using the name "Arachne" in 2006's "Ms. Marvel" comics.
Arachne's primary abilities include superhuman strength, agility and speed. According to the Marvel Wikia, she can lift at least 10 tons above her head, and can run faster than even the speediest professional athlete. She recovers from injuries faster than normal humans, and can exert herself for hours without growing tired. She also possesses superhuman reflexes, allowing her to react to danger much more quickly than a normal human being. Poisons and other toxins have absolutely no effect on her.
Like a spider, Arachne can sense vibrations through her touch, allowing her to sense approaching objects and detect anomalies such as hidden compartments in walls and floors.
A number of Arachne's powers are mental in nature. Chief among them is the ability to generate "psi-webs": strands of ambient energy which she can use to swing from or bind her enemies. This constitutes a major difference in her abilities from Spider-Man, whose webs are a scientific compound that he fires from wrist devices. Arachne can create her webs remotely and controls them via mental command, which Spider-Man is unable to do.
Like Spider-Man, Arachne can stick to walls by using her hands and feet, climbing and descending vertical surfaces with ease. Unlike Spider-Man, these abilities stem from her mental powers and not a radioactive mutation.
In addition to her "spider-like" mental powers, Arachne possesses more traditional mental powers. They include the ability to predict the future (or at least parts of the future), to communicate telepathically, to psychically sense remote events, and to project her consciousness outside her physical body.