These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Complete Monster: Following his resurrection in the nineties. Once a Tragic Villain who suffered from a Split Personality that forced him to become the Green Goblin, Norman was apparently slain after he threw Spider-Man's girlfriend, Gwen Stacyoff a bridge, in what many fans saw as his Moral Event Horizon. Brought Back from the Dead in the nineties, Norman revealed that he had been the mastermind behind The Clone Saga, buried Aunt May alive and killed Peter's clone, Ben Reilly, while gloating that he could now remember all the crimes he'd committed as the Goblin and was proud of them. Since then, he has gone on to be a major player in the Marvelverse, masterminding the creation of the Dark Avengers. During this time period, he kept the Sentry in line via drug addiction (then had his wife killed), planned to have the captured Songbird decapitated (so that he could mount her head on the wall and masturbate to it), and deliberately triggered a war with Asgard by having the U-Foes attack Agardian warrior Volstaag in a football stadium, resulting in thousands of casualties. During this time, he also seduced and impregnated his son Harry's girlfriend, then plotted to have Harry killed, because he thought Harry's tragic death would earn him public sympathy. These, by the way, are all actions committed by the Norman Osborn persona; the Green Goblin persona remains an Axe CrazyMad Bomber who regularly endangers/kills hundreds of civillians during his battles with Spider-Man, and, in commemoration of Gwen Stacy's death, tried to recreate the tragedy with Mary-Jane Watson, Peter's then Love Interest, as the victim. As Norman Osborn he's a cold-blooded, calculatingpsychopath who treats everyone as a means to an end. As the Green Goblin he's a violent lunatic who threatens every person in the vicinity.
Moral Event Horizon: The murder of Gwen Stacy is almost universally agreed to be when Norman crossed it, and perhaps the second most infamous murder in Spidey's history (following Uncle Ben's demise). It was extremely jarring to readers at the time because it was the permanent deathof a main character.
The Untwist: Him being the Goblin King. Slott spent a lot of time teasing the idea that it might not be Norman, and had him refuse to unmask, in what really served no purpose but to raise suspicion that it might not actually be Norman. In the end, nope, its Norman, and him refusing to unmask pretty much served no purpose what-so-ever because of it.
Newer Than They Think: Thematic example. In Revenge of the Green Goblin Osborn, his son Harry then long dead, started to realize that Peter himself was everything he ever wanted in a son and heir- smart, resourceful, tough, and able to live through everything life throws at him. This was since retconned out of existence (partly because Harry is back, partly because Norman no longer knows who Spidey is), but it was well received and became an integral part of his character in other media, such as the movie and the Spectacular Spider-Man cartoon. Even Ultimate Spider-Man uses it to great effect (and when Norman's around, the series reallyforgets it's a comedy). So successful some more recent fans thought it was always an integral part of the character.