History
Harry Osborn was the son of Norman Osborn, who was killed by Spider-Man as Green Goblin. Harry hated Spider-Man for that, but he was also a friend of Peter Parker - the man behind the spider mask. But one day, Harry found out the truth about Peter and used his father's old goblin toys to take revenge.
At first, he was very kind to MJ to make Peter angry and jealous, so he would come to sort things out with Harry. Then he attacked Peter as New Goblin, but was defeated. Some time later, he decided to have a rematch, but that time Spider-Man was in a black symbiotic suit, so he defeated Harry even easier. The further fate of Harry is unknown, but Peter joked that Harry wouldn't even remember who he was after such a beating. It's possible that Harry indeed lost his memory about the events.[1]