Dumbledore, notorious for giving second chances Dumbledore, let Sirius rot in Azkaban for twelve years.
He must have known Sirius well due to his time in the Order, he must have known what James meant to Sirius. Dumbledore was a member of the…
I normally avoid this sort of debate, but I have a lot of issues with this premise because I feel it misses an important factor: that Dumbledore is human, and has human failings. Too much of the criticism of Dumbledore is predicated on the naïve belief (which, granted, Dumbledore himself promotes) that he is in fact omniscient.
But this particular post bothers me because the entire argument that Dumbledore didn’t give Sirius a second chance is factually wrong. Dumbledore did everything he could to give Sirius a second chance, at Snape’s expense, after the Shrieking Shack incident. Sirius literally attempted murder. And Dumbledore basically covered it up because he saw Sirius’s potential and wanted him to have - yes - a second chance.
I feel it entirely reasonable that when Sirius seemingly did what he did, Dumbledore felt the human emotion of betrayal. Furthermore, he likely was attacked by a lot of guilt over how he’d handled Sirius’s first grave mistake, and decided that he’d already interfered enough.
Which also explains why he so readily accepted Snape - who was, after all, the one most harmed by his previous attempt to be “fair”. Snape at this point had only made one mistake of his own, and it was at least partially a direct result of Dumbledore’s own actions. So of course he wanted to give clemency - both to Snape and to himself.
Did Dumbledore do some morally questionable, even unethical things? Yes. But I think that the circumstances and motivations behind them are far more complicated than people often credit. He was in a unique, precarious position where every action had massive repercussions. Of course he made mistakes. And the fact that the books don’t shy away from that - the fact that we can even have this conversation - is, I believe, a testament to why he’s a great character.
(I also don’t even know if we know for sure that he was Head of the Wizengamot when the Potters were killed, do we? When we see his memories of the Death Eater trials, he seems to just be any other person sitting in the audience. It’s entirely possible he had not yet ascended to that rank. But that’s beside the point of my argument anyway.)