As one of Spider-Man's earliest and most formidable foes, Norman Osborn has taken many forms in his constant quest for vengeance and dominance. Jumping between the roles of the feared businessman and the Green Goblin, Norman has been able to use the powers at hand to ruin Peter's life at every opportunity. At one point, he even took the role of the Iron Patriot, leading his own version of the Avengers team. In this false armor, he managed to nearly gain control of the entire Marvel universe. However, Osborn's most dangerous form came when he merged with the Carnage symbiote -- turning him into the Red Goblin in San Slott and Stuart Immonen's Amazing Spider-Man #798 in 2018.
Following his rise as the Goblin King, Norman managed to take control of all of New York's crime under the watchful eye of the Superior Spider-Man, Norman's defeat ended with a series of nanites being injected into his bloodstream. Utilized by the original Peter upon his return, these nanites canceled out the effects of the Goblin serum, effectively removing Osborn's long-held madness. At first, Osborn thought his sanity could finally be the tool that gave him victory, but that also failed to pan out. He was now desperate to regain his insanity. Trying magic as a first attempt, Osborn's resources led him to Carnage.
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Merging with the symbiote, Osborn regained his insanity and offered his intelligence to the symbiote, creating a deadly and efficient killer. For his opening act, Norman, in his usual green identity, attacked the Daily Bugle and planted a bomb in an effort to lure Spider-Man. A standard battle between the two began, as Spider-Man worked to evacuate his coworkers. However, when the bomb exploded, he only managed to protect himself, as Norman took on the full force of his bomb. Finding his impaled body, full of debris, Peter thought for a moment that the rivalry between the two had come to an end. At this moment, Osborn revealed his new form and the first of many power upgrades. As the Red Goblin -- and with the symbiote flowing through his veins -- he could heal instantly from any fatal injury.
At the same time, Norman also showed to have greater control over the symbiote. Pursuing Spider-Man through New York, his array of pumpkin bombs were also infused with the symbiote, giving them personalities of their own and the ability to both track their target and to bite them. These little bombs tore apart Spider-Man's leg, forcing him to hide away from Osborn's wrath. Osborn hoped that his newfound power would scare Peter from ever wearing the mask again. In addition, Osborn's control prevented many of the symbiote's usual weakness from making an appearance. This meant that the Red Goblin was impervious to both sound and heat.
On a rampage, the Red Goblin could also split his symbiote into other parts, keeping control over the disparate elements. Using one portion, Osborn managed to corrupt his grandson, Normie, and turned him into a miniature Red Goblin that he would send to kill Aunt May. After many of Spider-Man's allies attempted to intercede on his quest for revenge, it was revealed that every scratch from the Red Goblin left tiny shards of the symbiote within his opponent's blood. Using his control, Osborn could send those shards into each of his victim's hearts, killing them in a moment. Thankfully, Flash Thompson's new role as Anti-Venom saved their lives, with his own cures serving as the Red Goblin's only weakness.
This battle proved to be one of Spider-Man's greatest ones. Ultimately, it was Osborn's ego that led to his downfall, as he decided that he alone should be the one to kill his arch-enemy. This decision, and the choice to return to the Carnage symbiote, led him to lose his memory, instead believing himself to be Cletus Kasady. For a while, Osborn became tied to the symbiotes, eventually leading him to become a servant in Absolute Carnage. Now, Osborn has made his return and has been forced to witness the full tragedy and consequences of his actions that have ruined so many lives.