One of the most important litmus tests for Spider-Man media: When they portray Harry Osborn, do they do a good job?
I’ve seen so many conflicting versions of Harry that I can’t actually tell anymore.
Harry Osborn essential traits: Best friends with Peter Parker, wants to gain his father’s approval at the start of the arc, cares for his friends, can be very determined
Important to note that Harry is no super genius but he’s not an idiot. He’s someone Peter would consider a best friend, and at his core is a decent person. Harry’s far more compassionate than his father. Given his usual story arc, it’s no surprise if he wants to kill Spider-Man for revenge for his father’s death. However, Harry is not the sort for killing others as collateral damage or just to hurt Peter (and even when he has Peter at his mercy, Harry can’t bring himself to kill him). Harry and Peter share a lot of friends, so Harry wouldn’t want to hurt Gwen or MJ.
It’s also important that Harry’s mental illness is well handled. @sarah531 can go into far better detail about it than I can, but Harry was- and is!- notable in comics because he’s a person with a mental illness that isn’t just a stereotypical cackling villain, but a decent person at core.
The cartoon Spectacular Spider-Man did his story pretty well, showing his drug addiction. Ultimate Spider-Man has a very different portrayal of Harry from usual, but it does a good job as well, though it doesn’t go into Harry’s drug addiction or mental illness from the comics. The Raimi films do a good job, with the revenge and redemption story.
The Amazing Spider-Man 2 did a horrible job with Harry, compositing him with his father and ignoring a lot of his best traits.