Severus Snape- a grey character! He was a Half-blood as his mother Eileen Prince, a pure-blood witch and his father Tobias Snape was a muggle. He had very unhappy childhood, he was friendless and even worse, uncared by his parents. His parents often fought with one another and thus Snape was neglected by them which made him so lonely that he just wished he could go to Hogwarts as soon as possible and leave this miserable life behind. Last summer of his eleventh before he could go to Hogwarts must have been so hard for him as he waited for it so long.
Lily was living in the same town as Snape’s and he noticed that she had magic in her. He had no social skills as he was alone for all he could remember and started talking to Lily Evans and her sister Petunia which freaked Petunia. Petunia didn’t like Snape as he had odd dressing. Snape told Lily that she was a witch and would receive a letter from Hogwarts.
Snape met James and Sirius on the train to Hogwarts and James disliked him as Snape was interested to go to Slytherin house and he got chosen into Slytherin house while Lily in Gryffindor house. He was a studious and introvert fgdggggggperson. He was so talented from the beginning that he knew better his seniors and had invented many charms, curses and potions during his study.
In his memory, we can see that James bullied him and insulted many times. When Lily tried to save him, he called her mudblood and she never forgave him for this. Snape was saved by James at life of his risk when he tried to go into the whomping willow after Remus Lupin as Snape noticed that Lupin kept disappearing every month. Snape did not tell about Remus as Dumbledore Swore him to secrecy. His bitterness towards James increased when Lily married James.
Snape joined Voldemort’s death eaters and told him about the prophecy that he eavesdropped but he heard only half prophecy as Aberforth caught him.
When Severus Snape found out that Voldemort is going after the Potter, which means Lily. He was terrified that he was the reason which put life of Lily in danger, so he pleaded Voldemort not to harm her; to which Voldemort agreed, but Snape was not stupid enough to believe Voldemort to keep his words and he went to Dumbledore. He asked to save Potters from Voldemort in return to do anything. Dumbledore asked him to spy for him in disguised as death eater. Despite every effort from Dumbledore, Voldemort killed Lily and James as their own friend Peter Pettigrew betrayed them. Snape lost reason his reason to live but Dumbledore asked him to save Harry as last wish of her love Lily who died to protect him. Dumbledore believed that Voldemort will return.
Snape started teaching at Hogwarts. He applied for Defence against the dark arts multiple times but was denied as Dumbledore knew that post was jinxed and no teacher could stay in that post more than a year. So, snape started teaching Potions classes and became head of the Slytherin house. He hated Harry’s resemblance with his father James Potter who bullied Snape but still he was the child of the women he loved. He has to act like that a person who is still on the dark side so that when Voldemort comes back to life, he can show and get Voldemort’s trust. Of course, Voldemort can’t access Snape’s true mentality despite being the greatest wizard as Severus Snape was powerful too. But still Snape has to show something, he can not just say to Voldemort that I don’t want you to see my mind and just believe my words, can he?
Yes, we can all say that Snape treated other students like Neville badly or favored Slytherin students, but he is a grey man and I don’t want to argue about him being good or bad. He never missed the chance to punish Harry but at the same time he never hurt him badly, even saved Harry’s life from many dangers. This doing, helped him to get Voldemort’s trust so easily as Snape was with Dumbledore many years, so he had knowledge about Dumbledore and Order of the Phoenix.
In the Half-blood prince Snape agreed kill Dumbledore because Dumbledore was already dying from the curse activated by the horcrux ring which was spreading to his body and he would die a painful death anyway.
One thing many people don’t know because movie did not show them. That is Severus Snape continued taking orders from Dumbledore’s portrait in the headmaster’s office. Upon Dumbledore’s order he gave the Gryffindor’s sword to Harry with the help of his Patronus. It was Dumbledore who suggest Snape to tell Voldemort the real date and time about Harry’s transfer to the Burrow to get trust of Voldemort. While moving seven potters, Snape accidentally hit George’s ear while aiming for another death eater.
Snape was hated by most of his students and even by professors as Harry told him that he killed Dumbledore at the astronomy tower. Snape had a fight with McGonagall and other professors and had to flew as they overwhelmed him. He could fly without a broom just like Voldemort.
At the night of Hogwarts’s battle, Voldemort summoned him to shrieking shack where Voldemort was hiding with Nagini the snake. He told Snape that his wand is not obeying him. The wand is working like a normal wand and not showing the power that it should. Voldemort believed that Snape was the true master of the elder wand as he killed Dumbledore and owned the elder wand. The wand will not obey him while Snape is breathing and he kills Snape mercilessly.
At the last moment of his life, Snape gave harry his memories with Lily and with Dumbledore that he has to do at the last moment. He asked Harry to look at him so that he could see Lily’s eyes for the last time.