Hateful

It had always been easy for Sirius to hate Severus Snape. The loathing started their first day at Hogwarts, when the sullen boy was sorted into Slytherin while the heir of the House of Black went to Gryffindor. Sirius was secretly relieved, and happy with his roommates, but when the Howler arrived from his mother calling him worthless, he focused his anger on that greasy upstart. He resented it, too, when Snape proved to be good with potions and better than Sirius at Defense Against the Dark Arts, though this might have had something to do with the fact that Sirius rarely studied.

It didn't help matters any that their names were so similar, and that once in a dark hallway, a girl behind him who was paying attention only to his hair color had mistaken him for Snape...as if that underfed boy could have had anything in common with him. It also didn't help that Remus thought Snivellus was smart. Remus objected, privately, when Sirius and James had a laugh at Snape's expense. Why did Remus care?

Sirius wasn't really thinking of killing Snape, exactly, when he goaded him into the tunnel, just that Snape deserved to be taught a lesson. A prank, that was all it was ever meant to be, even though it took months to convince Remus to trust him again. Of course it would have been awful if the wolf had attacked a student -- it was bad enough that Snape knew, afterward -- and if Sirius hadn't been thinking about the possible consequences for Remus, it was only because Snape made him so furious, with all his poking around and getting in the way. Sirius hated Snape for that more than anything.

He was complacent when he heard that Snape had become a Death-Eater, even though he suspected Snape might be a dangerous enemy. Hearing that Snape had turned somehow validated the years of despising him and treating him like rubbish, as if the turning had been inevitable...certainly not something that he and his friends might have encouraged with their cruelty. When Snape left Voldemort's followers, even though he earned Dumbledore's confidence, none of the others ever really trusted him -- not even Remus.

Then, after the biggest mistake of Sirius' life, Snape was always a safe thought. For surely Snape must have had an inkling about Peter, and if Dumbledore kept him at Hogwarts, then he must have known things that could have made everything happen differently if only Sirius had known them. James might have lived. Harry, that boy who existed only as a vague idea, no identifiable face, no remembered voice, might have grown up with his parents. And Remus might have been with Sirius, or at least speaking to Sirius, sending him OWLs, remembering him. If Remus no longer loved Sirius, it was all Snape's fault.

In Azkaban, despising the turncoat sustained him. But it had always been easy for Sirius to hate Severus Snape. It was easier than hating himself.