The Harry Potter series shows us some awesome but realistic portrayals of friendships. Harry himself is best friends with Ron Weasley, a boy from a poor background who often is jealous of Harry's fame and money. Despite this, he sticks by Harry's side — most of the time, at least.
But there are times that despite Ron doing his best to be loyal, his jealousy and insecurity gets the better of him and he ends up doing things to his best friend that Harry simply does not deserve. It's a realistically portrayed friendship, with the ups and downs of teenagers who don't always hold on well to their emotions and process them as they should.
Best: Went With Him To Get The Sorcerer's Stone
When Ron was only eleven, he went with Harry to get the Sorcerer's Stone away from Voldemort and sacrificed himself to the chess pieces in the process. Ron had only known Harry less than a year and did not have a personal nemesis in Voldemort the way Harry did but even at eleven he was willing to risk his own life because he knew it was for the greater good; and that his best friend might die if he didn't. That's pretty much the best friend you could ever hope to have, at that age or any age.
Worst: Didn't Stand By Him During The Triwizard Tournament
But when Harry was up to compete in the Triwizard Tournament, Ron's jealousy got the best of him. Not all of the attention Harry was experiencing was positive — in fact, most of it was not — but Ron still turned a blind eye to it and convinced himself that Harry had submitted his name himself, that he actually wanted to compete, and that he had not confided in Ron.
It was the insecurity of a fourteen year old boy, but it was still a blow to Harry who needed his best friend more than ever.
Best: Went To Get Horcruxes With Him
But at the age of seventeen, he undertook the most dangerous mission ever: the Horcruxes. Pieces of Voldemort's soul were scattered around the country and he went to go find them, despite knowing they would be tortured and killed if caught and that the odds were stacked against them. It was partially for the good of the world, which was slowly falling apart thanks to Voldemort's ever-increasing hold, but it was mostly so his best friend didn't have to do it alone. Not many people would show such bravery.
Worst: Flew To Hogwarts In The Flying Car
Ron nearly got Harry expelled once, though. He convinced him it was a good idea to take the flying car to Hogwarts.
Alright, Harry wasn't difficult to convince. But Ron knew the risks more than Harry, with a father in the Ministry and much more knowledge of wizarding world laws than a boy who grew up with Muggles and had only been aware of this world for a year. He should have been the one to say such a journey was too risky, let alone convince Harry to accompany him on it.
Best: Used The Same Car To Rescue Him
But he did make worthwhile use of the car, once. He used it to rescue Harry from an abusive home when Harry was not replying to his letters. Knowing something was wrong, Ron flew the car to the Dursleys along with his brothers Fred and George and they broke Harry out of the house he was locked up in. This flight was just as illegal, of course, but the end justifies the means.
Worst: Abandoned Harry (& Hermione) During The Horcrux Hunt
Ron may have gone Horcrux hunting with his best friends, but he did have his doubts, and they led to him leaving.
After growing frustrated and afraid, he abandoned Harry and Hermione in the middle of the forest alone and went back to his family. It was a very human move but still an awful one, because it left his two best friends with less help than they had before and feeling absolutely awful. Not only was this a blow for Harry, but it was a worse one for Hermione, who was definitely in love with Ron at that point.
Best: Gave Him A Life Outside Of The Dursleys
Ron gave Harry a life, family, and home outside of the Dursleys. He knew Harry's blood family were abusive and neglectful, and he always welcomed Harry into his home and shared what little he had with his best friend. In general, that was a selfless thing to do since it wasn't like they had much room in the home or money for food (and magic can't conjure food out of thin air, as J.K. Rowling has asserted).
Worst: Accused Him Of Being With Hermione
Ron did, out of jealousy, once accuse Harry of being with Hermione. It was an irrational thought, since Harry had always thought of Hermione as a sister, and told Ron as much. But Ron let his own insecurity get the better of him and at a time when so much was more important, he accused Harry and Hermione of having been in a secret relationship or at least secretly lusting after each other.
Not the best time to have that fight during a Horcrux hunt, but okay.
Best: Defended Him At Hogwarts
Ron wasn't always on Harry's side during his fourth year, but when he was, he went hard. When people accused Harry of having put his name in the goblet and Ron realized how ridiculous it was, he defended Harry hard. He also went to bat for him when people accused him of being the heir of Slytherin, desperate to protect his best friend who truly needed the .
Worst: Implied He Enjoyed His Fame
But perhaps the worst thing, at least for Harry, is when Ron accused him of enjoying his fame; of milking it. Harry always hated his fame, found the attention uncomfortable, and felt guilty about Ron's jealousy. Ron's accusations were not okay and came from his own problems rather than anything Harry was giving off, and he really needed to take a second to check himself.
Which, thankfully, he eventually did.