Snape and Lucius likely worked together as Death Eaters during the First Wizarding War.

The evidence shows that Snape is effective. Calling Snape a good person would be a little extreme as he was a really nasty teacher, some may argue that he didn't choose that profession and was a teacher so he could carry out Dumbledore's plan, but terrifying someone so much to become their worst fear cant be sidelined. Did Snape despise Sirius so much that he’d let him be tortured and killed? It didn't get twisted when she married James.

exams. Snape’s love for Lily kept him going through everything that was asked of him – he effectively gave up his life to act as a double-agent in the battle against her murderer. He can be a piece of shit when it comes to his outward mannerisms and ways in which he treats people, but he’s ultimately good under this veneer. Nevertheless, I doubt many people would say that Snape is a good teacher. Snape's love for Lily was really true love. Unbeknown to Harry, Snape made contact once the students left with Umbridge and they ought to have returned to the news that good old Snuffles was safe and sound. There are many reasons for this - 1. Compare with Dumbledore, who’s outward actions conceal from Harry that he was raising him to die at the right moment, a cold and calculated move for such an outwardly pleasant individual. He literally kills the one person who could reveal that he's actually a good guy.

One of the most touching things about his memories was how vehement he was that Harry must never know everything he had done – including all the good.

Of course not, but under no circumstances could they have brought that up in front of Dolores Umbridge.

That is why he has to define that his life really does serve a good purpose.

Snape is, at the end of the day, a good guy. Whether Snape is a good teacher depends on how one defines “good”. Most of his pupils pass their O.W.L. Lucius Malfoy was a Slytherin prefect when Snape began attending Hogwarts, and the two ran in the same social circles, which included other future Death Eaters. You can't tell me this didn't break Snape's heart and leave him entirely alone.

Snape appeared to be on good terms with the Malfoy family. Why is Snape considered by many a hero? Snape left his life of malevolence only to remain in darkness for the sake of the greater good.