The Order of the Phoenix is a notable group of witches and wizards who work together as a counterforce to Voldemort's Death Eaters. They assembled when Voldemort first rose to power, gathered together by Dumbeldore and those he trusted most.
They lost many in their fight against the Dark Lord. But after Voldemort was vanquished by Harry Potter, they were able to lay low for many years until Voldemort returned to power. We get to meet the reformed Order in the book and film series. For the most part, the Order was filled with popular characters who became heroes in the second great wizarding war. But sometimes they did some pretty terrible things too.
Sirius gave up being the secret-keeper
Before Peter Pettigrew was secret-keeper for the Potters, Sirius Black was. It made sense due to Sirius being James' best friend. Unfortunately, Sirius thought it was a wise decision to make Peter the secret-keeper because it would have been too obvious had he been the one conducting the Fidelius Charm.
But the plan backfires terribly as we learn Peter was a traitor to Voldemort. Honestly, this wasn't one of Sirius's smarter decisions. That said, it's clear he has been haunted by the mistake for his entire life. He thought it was the right decision at the time and unfortunately, it led to the demise of Lily and James Potter.
Dumbledore killed his sister
In the seventh book of the series, we finally learn the truth about Albus Dumbeldore's dark past. When he was younger, he engaged in a duel with Gellert Grindelwald that ultimately got his sister Ariana killed. It was a tragic mistake and like Sirius, Dumbledore has been haunted by it for his entire life.
He didn't intend to kill his sister, the entire incident was an accident, but we also have to understand the kind of person Dumbledore was back then. Grindelwald led him astray and his beliefs were fundamentally different from the man we knew. There was a time when he believed in wizard domination over muggles and more.
The Order didn't do a great job of helping Harry
Considering the job of the Order was to look out for Harry, at least during their second reformation, Harry went through a lot of trauma that adults could have helped him with.
The Order had assigned specific to watch out for him, even setting one person, a local squib known as Arabella Figg, in the neighborhood to ensure Harry was taken care of. But none of them exactly helped Harry avoid the years of emotional abuse he experienced by the Dursleys. Surely a group of skilled wizards could have done something to make Harry's life a little less miserable.
Snape was an abusive bully
Severus Snape is one of those characters that will have people fighting about his motives for years. But at the end of the day, Snape was an abysmal and terrible professor. It's shocking the Dumbledore let him get away with the constant bullying and belittling of his students for years on end. It doesn't matter if Snape was a valuable part of the organization, that didn't give him the right to be cruel to literal children and teenagers.
He sent Neville Longbottom into a nervous breakdown on more than one occasion. His hatred of Harry was unfounded and entirely based on bitterness at not getting to date Lily. He's a full-grown man child. Now, that said, most of the Order isn't to blame for this. It falls squarely on Dumbeldore's shoulders. The other were generally not keen on Snape either.
The Order somehow let a Death Eater teach
In the fourth book of the series, Mad-Eye Moody aka Alastor Moody, a professional Auror, arrives at Hogwarts to teach Defense Against the Dark Arts. Except we find out later that Moody never made it to Hogwarts. Instead, he was replaced by a loyal Death Eater named Barty Crouch Jr. Crouch who used his position to guide Harry Potter through the Triwizard Tournament so Voldemort could use his blood to perfect his resurrection.
How on earth did no one figure out something was amiss with Moody? It seems a little unrealistic that all these highly-trained wizards wouldn't have at least suspected something. Yes, we understand Crouch was skilled at his deception, but still. It's a little alarming that the Order could have missed something like that.
Why was Mundungus Fletcher tolerated?
Mundungus Fletcher's purpose in the Order of the Phoenix was somewhat similar to Snape's. Most of the didn't like him but he was allowed to be involved due to his sketchy connections to people who wouldn't have trusted or talked to the more honorable . That said, Mundungus was given some fairly important jobs which seems downright idiotic.
Why on earth would Mundungus have been enlisted to watch out for Harry? He's clearly not trustworthy and he vanishes at a moment's notice when a better deal comes along. As if that instance wasn't bad enough, they again trust Mundungus to help move Harry to a safe house and he disappears in the middle of the battle, leading to Moody's death.
The Order could have been kinder to Sirius
Sirius was difficult to deal with in the later books as he was mostly quarantined inside a house he hated due to his status on the most wanted list. When the Ministry turned against Dumbledore, things became especially difficult for Sirius. That said, the people of the Order could have been more understanding to what Sirius was experiencing.
He didn't have anyone to talk to that would truly understand what he was dealing with. Likely Sirius had a lot of trauma from his years in Azkaban that was never resolved. While he did have Harry, even he didn't reach out through the two-way mirrors Sirius gave him. Harry's reasoning for why makes sense but at the end of the day, the guy was very isolated and alone.
Keeping so many secrets from each other
There were so many secret agendas and plans within the Order it's a wonder they were able to get so much accomplished without overlap. The Order kept a lot of secrets from the wizarding world, but they also kept them from each other. Some things could have gone smoothly had there been better communication between them.
This also refers to Harry. A lot of the work in the Order related directly to him and yet he was kept in the dark because they didn't think he was "adult" enough or "mature" enough to understand things like the prophecy. It's pretty idiotic because had Harry known about the prophecy he might not have rushed there to save Sirius.
The Marauders took things too far as teenagers
When James, Sirius, Lupin, and Peter were all still kids at Hogwarts, we find out that they were bullies and that James was pretty arrogant. Harry is horrified by this discovery when he witnesses it in the Pensieve and Snape's memories.
Even though Snape would eventually grow up into someone who was even worse, it's still pretty sad to see that people Harry looked up to weren't exactly generous or kind to everyone while they were still in school.
Blind faith in Dumbledore
If you talk to anyone in the wizarding world about Dumbledore they have nothing but kind and overzealous words to say. Everyone believes he is the best wizard of their age and the only wizard that Voldemort has ever feared. No one ever questioned him.
They all blindly followed his lead regardless of what the demands were. We know later on that Dumbledore was essentially raising Harry for slaughter. He was a king of manipulation and even though his intentions were mostly noble, there is certainly some darkness to his character. It might not have been a bad idea for people to see past the veneer of wisdom to question what his motives were.
