If you thought Hermione Granger was smart, you’ve not paid attention to this character.
If you thought Voldemort was an ingenious Wizard, you’ve not given this character due credit as a Wizard.
If you thought Sirius Black’s resilience in Azkaban was the greatest display of character, this character goes beyond that even.
The character’s story starts with joining Hogwarts as a eleven years old kid.
Before writing more about this character, a recall of just how good Hermione was:
Hermione could read 450 pages of academic material within 20 hours, and then have complete recall; she could do all the charms, spells, and jinxes they taught them in class better than any wizard of her age; with her homework, she could go the extra mile, driven by curiosity, to find out that Professor McGonagall was an Animagus; she’d read every book she could to know as much as possible; when every other kid in her class struggled to get started with Transfiguration, she managed it with panache; by the time she reached the sixth year, she was already doing complex magic like ditching the dark magic radar while hiding in the forest.
Back to The Character. He is a eleven years old kid who walks into Hogwarts, the first year. He is quiet, reticent, and brilliant; but the day he walks into Hogwarts as a First-year fresher, he already knows enough not just to be better than his classmates, but he knows more magic than the second years, the third years, the fourth years, and even the final year students.
Think about that. A eleven years old kid walking into the room as not just the brightest kid in the room even before the room fills up, but as the brightest kid in almost all other rooms, age no bar.
The magic he knows so much more about isn’t just the commonplace magic. No. It’s the more complex dark magic that this kid knows about. Even Voldemort was in his finishing (school) years when he got curious about dark knowledge.
He’s the smartest kid, but he’s also reticent. Calm waters run deep? He doesn’t put his superiority on display for accolades.
He enjoys learning about the dark magic. Maybe he’ll turn into a dark wizard when he grows up.
But then, one day, he gets attacked by a group of wizards, all his school- and batch- mates. These attacking wizards are all smartasses, and they like to show it.
If he doesn’t do something to defend himself now, he might get killed. He’s interested in darkmagic, better at it than anyone else of his age around; it wouldn’t be past understanding that a young boy used some of that dark knowledge in the heat of the situation to defend himself when put in mortal danger — driven by adrenaline, or perhaps a deep-rooted desire to hurt people with dark magic; but no, he doesn’t use dark magic on the attackers even to save his life.
At an age where Hermione could do everything ( the school books said ) perfectly, he manages to do that not only equally good, but he goes beyond. He improves on the knowledge in the books.
Think about that: being smart enough not only to understand and practise precisely what the books teach you, but to be smart enough to spot mistakes in them, make corrections in the text, and invent your own spells.
All this while being a teenage school kid, without jumping at every opportunity to display his academic brilliance to stand out in the crowd. No. He’s all about being curious to learn, not about being the cynosure. Despite all his knowledge, he knows nobody likes an insufferable know-it-all.
Of course he loses his path, joins the dark side, realizes his mistake, and tries to make up for it by doing something so brave as to border on stupidity: doing something that doesn’t just require bravery, but also manipulating two of the greatest wizards, and creating and absorbing hatred toward himself so as to never be suspected of any other motive.
Beside the usual praise and criticism he receives, there’s still something sad about the fact that, to people who judged him, he was a man of other people’s words and gossip, not of his own actions.
Snape. Not just a brave lover, but also a brilliant and peerless wizard.
Footnote: if you think you've read this answer before on a Q&A site, you're right: this article is indeed written by the same person (who has chosen to share it here because of its relevance to our products).