Batman has the Joker, Superman has Lex Luthor, and I am going to go out on a limb and say that Spider-Man has Doctor Octopus.
Dr. Otto Octavius, or Doc Ock for short was a brilliant researcher who constructed a chest harness to which four artificial tentacle-like arms were attached to enable him to manipulate radioactive substances from a safe distance. In a freak laboratory accident, volatile radioactive liquids exploded, bombarding the scientist with radiation. The accident bonded his harness to his nervous system. Octavius received brain damage in the accident, causing him to become criminally insane. Octavius also found that he could now control his artificial arms psionically, rather than by the manual chest-plate controls. Over the years, Octavius gained an even greater command over his extra arms, enabling him to direct their actions even when they became separated from his chest harness. Surgery was used by the legal authorities to separate Octavius from the harness. The harness was again fused to his body by radiation at one point, but at present the harness is not fused to his body.
Doctor Octopus has sought to amass wealth and power through various criminal activities, and has formed gangs with which he has attempted to dominate crime in New York City. Although Octavius's original timid, benevolent personality returns from time to time, his sinister Doctor Octopus personality inevitably re-emerges and becomes dominant again. In fact, during one of his sane periods, Ock was engaged to none other than Aunt May. Fortunately the wedding was interrupted.
I should mention, during the clone saga in the 1990's Doctor Octopus was killed. He was replaced by one of his students Carolyn Trainer who took the name Octopus (she answered to both Doctor and Lady Octopus). She donned the mechanical arms as well as a force field. During this period, she clashed with the Scarlet Spider. Of course, Doc Ock was eventually brought back to life, and Lady Ock returned to him the tentacles and resumed her position as his assistant.
The two eight legged (in theory) creatures also duked it out in some awesome sequences in the film Spider-Man 2, and as usual, the web-head prevailed.
Spider-Man 3 debuts in 223 days!