Get ready for some Dumbledore slander. Like serious, Dumbledore slander. (!!Spoilers for Harry Potter books three through seven!!)
Ok, Dumbledore is a murderer. And yes, you might say, well, Harry Potter killed some people too, but no that’s different and I’ll tell you why. Dumbledore knew what he was doing. He knew that his actions would get people killed and that’s why I hate him for it. Especially in the Marauder era. He basically raised child soldiers to do his work for him. The worst part was the fact that he knew that Sirius Black was innocent and he just let him go to Azkaban? That makes literally no sense. You’ve blamed one of your students for something that you knew he was innocent for.
What’s even worse is the fact that Dumbledore potentially knew who the traitor was. He was the one who suggested that the Potters go into hiding, so he must have known where they lived. He told Snape because Snape still had feelings for Lily, and that’s why he knew where to go when Voldemort eventually killed James and Lily Potter. He also knew that Peter was the traitor, he knew that the Potters would get murdered.
And then he raised Harry just to basically sacrifice him later. There’s no way that Dumbledore didn’t know Harry was a Horcrux. Dumbledore even gave him the Snitch where the resurrection stone lay. He sent Harry to live with the Dursely’s instead of with Lupin, James’s best friend. Perhaps he thought that being around a werewolf was too dangerous, but there was no reason to not trust Sirus, Harry Potter’s literal godfather with the baby. It’s written in James’s will that Sirius will get designated care of the child. Even if Sirius was in a blind rage with Peter betraying them, he would have known that taking care of Harry was more important. Even sending him to live with Hagrid would have been a better idea than sending him to live with the muggle-born wizard-hating family that clearly abused him.
Dumbledore was also incredibly biased. Like horribly, biased. He only awarded points and attention to the Gryffindors, not caring about the other house members, and basically ignoring them. He was especially prejudiced against the Slytherins. So overall, Dumbledore was a crappy principal, a murderer, and a complete moron.