Albus Dumbledore is considered one of the most powerful and brilliant minds in the wizarding world. He was responsible for getting rid of the dark wizard Gellert Grindelwald and considered the only wizard that Lord Voldemort ever feared. During his time at Hogwarts, Dumbledore was a brilliant student and eventually a Prefect himself.
He became headmaster of the school and vital part of the story we all know and love about Harry Potter. But despite the way the book presents him, as a hero and one of Harry's greatest allies, there is much debate about Dumbledore's morality, motives, and his treatment of Harry throughout the series. In some ways, he gave Harry every tool he needed to defeat Voldemort, but in others he was certainly a hindrance.
10 Helped: Allowing Harry to break the rules to follow leads and grow as a wizard.
Many fans believe Dumbledore's intentions regarding allowing Harry to break so many rules without being expelled may have been foolhardy at best and dangerous at worst. But truth be told, it was always in Harry's nature to be a hero. He would have gone after the Sorcerer's Stone no matter what. He would have always found a way into the Chamber of Secrets and beyond.
Plus, when Harry truly needed Dumbledore to step in, such as when he faced off against Voldemort/Quirrell in the first book, he was there. But by allowing Harry, Ron, and Hermione to bend and break the rules from time to time, he was permitting them to gain valuable intellect, experience, and skill they never would have picked up in a classroom.
9 Hindered: Forcing Harry to take Occulmency with Snape as his professor.
Dumbledore's reasons for having Harry take on Occulmency lessons with Severus Snape as his professor may have been good in theory, but in practice the entire scenario backfired. While Harry certainly should have applied himself better and tried to keep Voldemort out of his mind, it stands to reason he would have performed better with a different professor.
Surely someone else at Hogwarts or in the Order of the Phoenix could have given Harry lessons. Even if they weren't as practiced at the art as Snape, it would have likely been more beneficial for Harry to work with someone who didn't utterly loathe him and vice versa.
8 Helped: Letting Harry have the chance to discover the Mirror of Erised.
In Harry Potter and the Sorcerer's Stone, Harry comes across the Mirror of Erised during a night time stroll through the castle. The mirror has the distinctive ability to show the person reflected acheiving the thing which they desire most. Harry sees his parents and family. Every night he is drawn back to the mirror to gaze into the future he missed out on.
Ultimately, it was a good decision for Dumbledore to let Harry find the mirror. Had he not, Harry might not have understood it when he found it again in the Sorcerer's Stone chamber. By understanding its purpose and the dangers of the mirror, Harry was able to use it to get to the stone before Quirrell.
7 Hindered: Giving Harry to the Dursleys as a baby without anyone to look out for him.
We learn Dumbledore's reasoning for making Harry stay at the Dursley's home on Privet Drive later on in the series. It was the safest place for him due to the blood protection shared between Aunt Petunia and Lily Potter. That makes sense. But what doesn't make sense is why Dumbledore let Harry be emotionally and verbally abused his entire life.
Surely he could have enlisted a few witches and wizards to stay in the area and keep the Dursleys in shape. It's been shown that they cower under threat of magic. Miss Figg was there and others kept a watchful eye on Harry, but no one ever tried to force the Dursleys to treat Harry better until well after he was already at Hogwarts. It's not like they weren't aware of the magical world so there's no real excuse for it.
6 Helped: Taking Harry on a journey to understand the Horcruxes.
Had Dumbledore simply told Harry about the Horcruxes, he probably wouldn't have had such a solid understanding of them, their uses, and Voldemort's intimate connections with the items he chose.
The journey that Harry and Dumbledore take in book six through various memories was a key element to Harry's ultimate understanding of how to bring down the Dark Lord once and for all. Reading about them wouldn't have rendered the same effect. Dumbledore's teachings and Harry learning about Voldemort's history was essential to killing him.
5 Hindered: Keeping Harry in the dark about the prophecy for such a long time.
For a long time, Dumbledore battled with whether or not he should tell Harry the truth about the nature of the prophecy made about him, or potentially Neville Longbottom, by Professor Trelawney. He kept putting it off and waiting and waiting until it was too late.
Dumbledore should have told Harry about everything after Voldemort returned in the fourth book. Had he done so, there is a good chance Harry would have been less likely to get lured into the Department of Mysteries and Sirius Black might even still be alive.
4 Helped: Not telling Harry the whole truth about Severus Snape.
This is a point of contention with many fans. Would it have been better for Harry to know the entire truth about Severus Snape or was it better that Dumbledore kept it from him? The relationship between Snape and Harry was never going to be warm and fuzzy. While Harry may have found a begrudging respect for him, he also would certainly have interfered with Dumbledore's plans.
Keeping Harry in the dark was also a smart move in regard to the fact Voldemort had access to Harry's mind from time to time. Had he seen anything but ire for Snape, it could have ruined the entire plan of having Snape play double agent. We also know that Harry has a weakness for being the hero. Would he have truly let Snape kill Dumbledore, even if he knew the reasoning behind it? Killing Dumbledore was pivotal in keeping Snape in Voldemort's graces and had Harry understood his motive, then it might not have been believable to the Dark Lord.
3 Hindered: Raising Harry to be killed by Voldemort.
No matter which way you look at it, by keeping Harry in the dark about the prophecy, it becomes more apparent that Dumbledore was using Harry like a weapon. He kept Harry alive at all costs so that he could face Voldemort and die by his hand. In the fourth book, Dumbledore has a "gleam of triumph" in his eye when he learns Voldemort took Harry's blood to regenerate.
He believed that by taking Harry's blood, that Harry would not need to permanently die. But still, it was only a theory. At the end of the day, Dumbledore was willing to let Harry die at the right moment and never told him.
2 Helped: Dumbledore did genuinely always try to give Harry the tools he would inevitably need.
Even though Dumbledore was something of a master manipulator, he still clearly did care about Harry and his students. He genuinely wanted Harry to succeed, and hopefully not permanently die at the end.
He tried to give him all the tools he would need along his journey. Even in his death, he left Harry the resurrection ring, the cloak, and gave him a way to destroy Horcruxes with the sword. But prior to that, he supplied other allies and tricks along the way too.
1 Hindered: Dumbledore never revealed his past or history to Harry.
Something that greatly upsets Harry in the final book of the series is the realization that he never knew Dumbledore, not really. At least he never knew anything about his past. He was forced to learn about it in a biography written by Rita Skeeter of all people. There were some dark and troubling reveals in that story.
For instance, there was a point when Dumbledore believed in Muggle domination due to his ties with Grindelwald. Learning about this is immensely upsetting to Harry, despite the fact it took place a century before. Had he learned this from Dumbledore and had the two had a more open and trusting relationship, maybe Harry could have been more at peace with his death at the end.