The question "Who is Spider-Man' arch Nemesis?" and the answer "More than two" are getting too old and senseless because it got way too obvious that "Norman Osbourn/The Original Green Goblin" is his arch-foe.
Since the day he started the Goblin made clever plots to smack Spidey to the ground, and wanted to seize control over crime in town to be the "Kingpin of crime" but his plans were always foiled by Spider-Man, this is why the Goblin remained hidden planning for his ultimate revenge.
The did not show the Goblins method of conviction to get the thugs use the bomb with the special formula that defunct Peter's spider-sense. The Goblin followed Spider-Man from a distance, learned so many information about him the fought him in the yard of his sick aunts and dragged him all the way to one of Osbourns warehouses revealing himself and have a fight ending with Norman forgetting the Goblin.
After seeing a slide show on Spider-Man & the Goblin Norman regained his memory and went to strike "May Parker", one of the Goblins gadgets made Spider-Man drows in fear and hallucinations
After getting back as the Goblin once again; he made attacks Peter in his apartment, throws a bomb of gas that made Spider-Man lose his ability to stick to walls when Harry was a drug addic, Spider-Man is forced to pull punches against his friends father, & Norman secretly had sex with Gwen making her pregnant with twins she give birth to in France before killing her and getting severly wounded with wounds he recuperates from later.
In his hideout in France Norman raised his twins making them believe they are Peters kids & made them despise him for abandoning their mother and allowing Spider-Man to kill her.
Harry Osbourn, and others after him; "Dr. Bart Hamilton", "Roderick Kingsley", "Jason Philip Macendale", followed Norman's footsteps and became Goblins while Norman was away in hiding.
The clone mess started by "Professor Miles Warren/The Jackal" was also a mess done by Norman to make Spider-Man insane and it did make him doubt how genuine he is for months.
"May Reilly Parker" was kidnapped and replaced by a genetically altered actress to resemble the original, she died and Peter grieved on her death for a while to be arrested for a murder committed by his un-cloned clone Kaine (I didn't read the clone saga, don't ask me how it happened)
Peter get exonerated eventually, Norman forced the Bugle out of Jameson to be owned by him. Not only that but he also talks on TV against Spider-Man turning the public against him worse than the way Jonah Jameson turned people against the wall-crawling masked menace.
As the "Green Goblin"; Norman talks on TV about the death of "Gwen Stacy" sounding a poor innocent man and Spider-Man is the actual murderous idiot.
Eugene "Flash" Thompson gets filled by the booze he wants to clean his blood from and is placed in a driven truck hitting the wall of his old school.
In prison; one guard asked Norman for a favor to save his sick wife only to have her condition worse, Norman told Spider-Man the story and planned for twelve sinister foes of Spider-Man to kill him after Spider-Man himself release Norman from prison directly.
Now Norman is seen as a patriotic national hero leading the Thunderbolts, and Spider-Man unregistered, wanted, and chased away by his internationally powerful foe