Just when everyone thought that he was safe, Rowling had the last laugh. Sirius only really became a proper godfather to Harry in TOOTP, for viewers anyway. There were moments in this film where you could see the bond that had been created between the two of them and the clear enjoyment that they have in one another's company. So when Sirius is taking from Harry, it's difficult to find anyone with worse luck than poor Potter. But what makes the aftermath of Sirius' death so shocking is that Harry runs off for revenge and actually attempts to use one of the Unforgivable Curses on Bellatrix. An action that Sirius definitely wouldn't have approved of.