Snape

Erroneously believing Snape is the master of the Elder Wand and that Snape's death will make him the master of the Wand, Voldemort kills Snape by having his pet snake Nagini bite him through the neck.

Despite this separation and Snape's enduring animosity toward Lily's eventual husband James Potter, Snape continued to love Lily for the rest of his life.

Dumbledore called Snape to help him; however, when Snape arrived and assessed the curse, all he could do was contain it.

During the confrontation, Snape reveals himself as the eponymous "Half-Blood Prince" (being the half-blood son of Muggle Tobias Snape and pure-blood Eileen Prince).

HBP Ch.28 The full relationship between Dumbledore and Snape and the reason for Snape's actions remain unknown until the final book.

In an interview, Rowling adds that Snape is immensely brave, and when asked if she considers Snape a hero, replied: "Yes, I do; though a very flawed hero.

In the final chapter, Dumbledore suggests that because Harry's father James had saved Snape's life when they were both students, even though the two detested each other, Snape felt responsible for Harry in return.

Later, Dumbledore assures Harry that Snape's reformation is genuine, though he refuses to tell Harry how he knows this, saying the information "is a matter between Professor Snape and myself".

OotP Ch.37 Harry still holds Snape partly responsible for Sirius's death, believing Snape's goading spurred Sirius into joining the battle.

Rowling further said in an interview that she wanted Snape to find redemption and forgiveness: "Snape is a complicated man.

Snape's memories also provide Harry with the information he needs to ensure Voldemort's final defeat, in the form of conversations Snape had with Dumbledore.

Snape was born to Eileen Prince, a witch, and Tobias Snape, a Muggle, making him a half-blood (hence the name, "Half-Blood Prince").

After Dumbledore's passing, Snape was instated as Headmaster — an appointment that was clearly arranged by Voldemort, who was very much in control at this point in time.

As revealed in the memories that Snape shares with Harry moments before he dies, Lily showed him kindness and was a friend when they were kids.

Despite what Severus Snape said about him, Harry Potter proved himself to be a powerful wizard.

However, Draco Malfoy was the Elder Wand's master, as he had disarmed Dumbledore before Severus Snape killed him.

However, others believe that Snape was a bad person because he was to blame for the death of Harry's parents (as he gave Lord Voldemort the prophecy that ended with Lily and James being murdered), and he was an abusive teacher.

In one instance, they even sent Snape to Lupin while he was in his werewolf form, risking his life but never facing consequences for their actions.

It turns out, Severus Snape outed him to Slytherins at breakfast and quite obviously, this news spread like wildfire.

Like Harry, Severus Snape saw Hogwarts as his only escape from abuse.