Past (in the comics)
Harry Osborn was the son of wealthy industrialist, Norman Osborn, the original Green Goblin. He went to the same college as Peter Parker, aka Spider-Man. They were roommates for a time, during which Harry encountered occasional problems with drugs. When his father died, Harry found the body and removed the costume.
After learning that Peter was Spider-Man he donned his father's costume and proclaimed himself the Green Goblin. After destroying Peter's apartment in a battle with Spider-Man, he began seeing a psychiatrist who tied him up and became himself the Green Goblin.
Harry later suffered from amnesia, forgetting the identity of Spider-Man and both his and his father's roles as the Green Goblin. Harry later married Liz Allen, an old high school friend of Peter's and had a son, Norman.
This tranquility was shattered when the aftereffects of the Inferno crisis sundered the barrier between Harry's conscious and subconscious minds. Once again, he remembered being the Green Goblin - and his irrational hatred of Spider-Man. Harry had convinced himself that Peter resented the Osborns' "stable family life" due to never having been wanted by his own parents or guardians, when in fact the complete opposite was true. His sanity was shattered, he declared that their next confrontation would be their final one, and only one of them would be alive at the end. To ensure that he was the victor, Harry researched his father's chemical notes, hoping to recreate the original Goblin's superhuman strength. Harry made his own modifications to the formula, and upon ingesting it, it proved better than he had dreamed. The formula had made him stronger than both Spider-Man and his father. Now a physical match for Spider-Man, Harry planned his final revenge.
For the first quarter of the movie Spider-Man 3, Harry was the main antagonist. During the second quarter, he becomes the tertiary antagonist. In the final half of the movie, Osborn becomes the deuteragonist, and helps Spider-Man defeat Venom and Sandman.
In the movie, Harry became the second Goblin after he stumbled upon his father's secret lair of Green Goblin paraphernalia. Harry's Goblin suit differed from the original suit in that it was black as well as green, and had a different, less threatening but more practical face mask, a long, snowboard-like glider-called the Skystick-and some different weapons. Harry sought revenge against Spider-Man for 'killing' his father, and attacked Peter Parker, as he knew of his identity. During their first battle, Harry was knocked unconscious and lost his memory. It was later restored however, when the vision of Norman Osborn appeared to him and reminded him of his vengeance quest. Harry once again attacked Peter, this time through Mary Jane. Harry later on redeemed and died.
Amazing Spider-Man 2
The Green Goblin (real name Harry Osborn) is the main antagonist of the 2014 film The Amazing Spider-Man 2.