In the Wizarding World of Harry Potter, few wizards even come close to Albus Dumbledore when it comes to magical might. The former Hogwarts headmaster had the beating of both Voldemort and Grindelwald: the two most deadly dark wizards of all time. However, just because he had a strong grasp of magic and a kind smile, that doesn't mean that Dumbledore was a good person at heart.
Nobody can deny that Dumbledore performed some incredible deeds during his lifetime and helped to improve the Wizarding World in many ways. Unfortunately though, not all of his actions were quite as heroic as others. In fact, some of the things that he did in the Harry Potter books and movies were downright devious. These are the worst things that Dumbledore ever did.
5 He Repeatedly Put His Students in Danger
Even ignoring Dumbledore's reckless decisions to allow dangerous magical beasts to be kept on school premises, the former headmaster's poor judgment when it comes to protecting his students is pretty alarming. For starters, he brings the Philosopher's Stone into Hogwarts despite knowing that certain people would happily kill to get their hands on it. Then, just for good measure, he leaves the school unattended right when it matters most.
The following year, Dumbeldore refuses to close the school despite the Chamber of Secrets being opened for a second time. Given that a student died the last time this happened, closing the school should have been his number one priority, yet he does everything in his power to prevent it from happening. Considering his talent as a Wizard, it's also a little surprising that Dumbledore didn't find the chamber at some point during the fifty years between it being opened, suggesting that he probably didn't look too hard for it.
4 He Sent Hagrid and Maxime to Parlay with the Giants
Neither book readers nor movie viewers are provided with too much information about giants, other than that they're incredibly dangerous and were once allied with the Dark Lord. With this in mind, Dumbledore's decision to send Hagrid and Madame Maxime to negotiate with them is incredibly reckless, especially as old Rubeus no longer has access to a fully functioning wand due to Dumbledore allowing him to go to prison for a crime that he didn't commit.
As it turns out, giants weren't the only thing that posed a threat to the expedition either, as Dumbledore likely knew all too well beforehand. The Death Eaters were also hoping to recruit the giants to their cause, and the two half-giants very nearly fell victim to their spells and curses after being caught off guard. Things could have very easily turned out differently though, not that Dumbledore would have cared too much.
3 He Abandoned His Family
It's often said that with great power comes great responsibility, and Albus Dumbledore was about as powerful as they come. Unfortunately, however, rather than using this power to protect his incredibly vulnerable family, a young Albus instead abandoned all responsibility to pursue power with his friend and possible lover, the dark wizard Gellert Grindelwald.
Even after the death of his sister and the increasingly obvious signs that Grindelwald may not be such a good guy after all, Dumbledore delays confronting his friend for as long as possible despite knowing that he is the only person capable of stopping him. Presumably, many more people will have suffered and maybe even died due to this delay, and it's all because of Dumbledore's selfishness.
Interestingly, this is one of the only things that fans ever get to see Dumbledore truly remorseful about. He openly blames himself for the death of his sister, and it's his guilt and remorse for this that ultimately leads to his death. After all, he wouldn't have put on the Horcrux ring and gotten cursed if he weren't so desperate to see her again. What's more, his decision to reward Neville with ten points for standing up to his friends in the first book/movie suggests that Dumbledore still hasn't forgotten how difficult it can be to confront a friend or loved one.
2 He Raised Harry to Die
All things considered, Dumbledore's treatment of Harry is pretty appalling. Right from the get-go, he leaves him in the care of the Dursleys despite McGonagall questioning their suitability as caregivers. Even after more than a decade of abuse, Albus leaves Harry with this vile family rather than simply applying the same spells and protections to another place of residence with more suitable caregivers. Knowing about this rampant child abuse and doing nothing to stop it makes him just as bad as the abusers. As it happens though, this was all just a glaring sign of things still to come.
Upon learning of Voldemort's use of Horcruxes, Dumbledore quickly deduces that Harry may well be one of them, yet never thinks to warn the young wizard. Granted, he may have been worried that informing Harry may have alerted Voldemort to the pair's connection, but he could have at least tried to remove or destroy the piece of Voldemort's soul rather than allowing it to lay dormant. Ultimately though, he appears to have adopted his old friend Grindelwald's "For the Greater Good" mentality once more, resigning himself to the fact that Harry must die so that others may live.
1 He Asked Snape to Kill Him
On the surface, Dumbledore asking Snape to kill him may seem like a selfless act, but it's actually emblematic of his mistreatment of poor Severus over the years. Having first used Snape's grief to manipulate him into a lifetime of servitude, Dumbledore then effectively sentences him to death by attempting to have him become the master of the Elder Wand. After all, he must have known that Voldemort would eventually kill Snape to become the wand's true master. Worse still, it's not just death that Dumbeldore condemned Snape to, but also infamy.
There's no way that Dumbledore could have possibly known that Harry would have been there at the moment of Snape's death. Had he not been (or had Voldemort killed him before he got the chance to tell anyone about Snape's heroics), the world would never have known about Snape's sacrifice and bravery. Just to rub salt in the wound, Snape dies believing that Harry was destined to share the same fate; effectively making him believe that all of his sacrifices were largely in vain.