Snapedom

It's hard to get beyond the premise of this question. Nothing we saw of Snape indicated that he was capable of truly horrifying acts. (Indeed, we were not shown that the Death Eaters as a rule engaged in wholesale, prolonged violence, with the exception of Voldemort, who used Cruciatus and other damaging magic, and unhinged followers like Bellatrix Lestrange and Barty Crouch.) Snape was only known to have sneaked around and spied. He otherwise slithered out of action, according to Bellatrix. As a student, he seemed more of a hapless victim than someone who injured others, no matter the "just you wait" spell he invented. His knowledge of the Dark Arts was only used in aid of others. Sure, he was mean to a few kids a few times. To me, that was never a big deal. I got over that sort of thing with teachers as a child. On balance, even though his approach wasn't always pretty, Snape almost always told the unpleasant truth and worked for the welfare and betterment of others. JKR may fixate on that "not nice" stuff to judge her character, but I think she gives him a bum rap.

But what if...? I wrote a story where Snape had done more evil as a Death Eater than I really thought he did, brewing a destructive potion and testing them with the same detachment our scientists use to test chemicals on animals. I quit a job because of the callous attitude towards life on the part of scientists I was working with... and, of course, their work was all in the name of saving lives. Yet, I don't hate any of those scientists. I don't admire or support them, but that is something else. I wrote Snape as the creator of a biochemical warfare-type potion partially to explore whether he could create something like that and be forgiven. In my story, he mouthed Manhattan Project-type justifications that would make his actions acceptable in war (this will serve the greater good in the long run, I'm not the one unleashing it on human populations) and in many scientific communities (I'm merely testing interesting concepts and expanding our knowledge), but my Snape never forgave himself, was never less than honest about his past, and always tried to mitigate the harm he might cause. He wasn't necessarily graceful to others in his actions, not forgiving of others' weaknesses, but I love the character with his flaws as well as his strengths.

I guess the larger meta question is, can one forgive a torturer? What of the soldiers at Guantanamo depriving prisoners of sleep, quiet, and warmth, playing mind games like Russian Roulette, beating and perhaps even water-boarding detainees? An individual asked to inflict these abuses may have the option to leave, although I know not at what cost. But if soldiers do not leave, should we not forgive them? This is a tremendously difficult question to answer, especially when soldiers do many horrendous things these days and are told it is part of their missions, or serves to make the world safer, or is just part of their job. I could give you my personal thinking on this subject, but it's quite complicated and here might not be the place.

In the end, Severus was trying to do what he felt was right, but he was a follower of men who routinely lied and abused others. Further, he accepted that he couldn't save everyone. (The only reason Harry saved everyone was because Rowling said he could, based on the lie Voldemort told.) Should Harry have taken himself out of the action and ultimately given up his life while others suffered? Should Severus have sat there and let Voldemort kill Charity Burbage? What would you have done?

I felt so bad for Snape in that scene. The requirement to follow Dumbledore's plan overrode all other considerations. Both Harry and Severus were following orders to the extreme, in Snape's case, possibly against his conscience (in terms of killing Dumbledore or watching others die). I think Harry's forgiveness of Snape partially grew out of their shared "following orders" situation. Of course, those orders were Dumbledore's. Did Harry forgive Draco for following Voldemort's orders?