SPOILERS FOR ALL HARRY POTTER BOOKS. - If you need this warning, where have you been? -
Severus Snape is the most controversial character author J.K. Rowling wrote in the Harry Potter Series. To this day, many years after the final book, fans still debate the question of Snape's real character. Was he the hero of the story or was he the villain? The best way to figure it all out is to break it down and see what we think of him overall.
We learn over the course of the series that prior to attending Hogwarts Snape was in a bad situation at home. His mother had married a muggle and their home lacked the love all children deserve. We know he met Lily Evans before coming to Hogwarts and she was really his only friend. Once he got to Hogwarts, we know that Snape's friendship with Lily continued and he claimed to love her deeply. James Potter, Sirius Black, Peter Pettigrew, and Remus Lupin (all four also known as The Marauders) bullied and tortured Snape for being a Slytherin, for his appearance, for his lineage, and for many other things. Severus Snape made one single mistake and called Lily a slur. This, in turn, damaged their friendship. Lily went on to marry James Potter who had been pining after her for years. After Hogwarts, Severus became a Death Eater serving Lord Voldemort (Tom Riddle) but did not understand the depth of what was required. After Lily's death, at Voldemort's hand, Snape became the Potions Master and Professor at Hogwarts. He began a secret mission to protect the only thing that remained of his beloved Lily, her son, Harry Potter. Severus essentially changed his mind and became a spy for Albus Dumbledore.
During Harry's time at Hogwarts, Severus Snape did a great many things. Some of them were not so good, while others were downright despicable. These are the arguments I always hear about how BAD Snape was. I have also included my thoughts and why I still think Snape may have been more than meets the eye.
People will say that Snape was a bad guy because he joined Voldemort...
Severus With Voldemort/ Death Eaters
But I think this was something different. If you consider what we know about Severus childhood, he had no friends. Once Lily wrote him off he was essentially alone. We know that Lucius Malfoy is the one who introduced him to Voldemort, but we don't have the specifics. I feel like Severus joined the Death Eaters because he wanted to fit in. He wanted a group who would have his back no matter what. Once he realized what Voldemort was really doing he tried to get out, but couldn't.
Some might say Snape is the reason Lily is dead...
Snape Mourns Lily
I disagree. I feel like even if Snape hadn't told Voldemort the bit of prophecy he heard, the Potters still would have been attacked. They were known loyal members of the Order of the Phoenix and if you remember, Voldemort was attacking known Order members trying to figure out what Dumbledore knew and what the Order's plans were. Lily and James would have been attacked eventually either way. They may have lived, but they may have ended up like Neville's parents, which I personally feel is worse than death.
People might also say Snape was a bully for harassing Neville Longbottom... And Hermione Granger... and Harry Potter...
Severus Snape as Neville Longbottom's Grandmother
I feel like there are reasons for this though, that while not making up for Snape's actions, do explain them.
Neville was one of the two who, in the prophecy could have been the "boy who lived" had Voldemort chosen differently. I feel like Snape was trying to make Neville stronger by always being on his case. If Neville could survive day after day of Snape's torture, he might just survive the upcoming battle.
With Hermione, Snape told her she was a know-it-all once in front of the whole class. He even insulted her teeth size after a jinx had gone wrong. I feel like Severus was trying to show her that not everything can be learned from a book. That sometimes things in life go badly and you have to make a choice about how to handle them.
Snape's grudge against Harry is pretty self-explanatory. Since everyone said Harry looked mostly like his father, Severus was stuck seeing James Potter, who tortured Severus for years, all the time. Would you be totally cool with seeing the person who married your only love every single day for years on end? No! You wouldn't. I also feel like Snape knew that if he was super nice and friendly with Harry the Death Eaters' kids would report back to their parents. Can you imagine Draco complaining to Lucius that "Severus was nice to Potter today," and it getting back to Voldemort? Yikes!
The other argument is Snape killing Dumbledore makes him the villain...
Dumbledore's Fall (Death Scene)
I feel Snape had no choice here. Let's say for argument's sake that Snape ignored the dying man's wish and didn't kill him. If things still happened in the say way as they did without Severus making the final blow, he would have been ousted as a traitor much sooner. Bellatrix or another Death Eater would have killed Dumbledore and Snape would be dead too. Because of his unbreakable vow to Narcissa Malfoy to help Draco and completed his task, of killing Dumbledore, if Draco could not, Snape would be dead without following through. So, if Snape is dead that means in Deathly Hallows, the Carrows are running Hogwarts, torturing all the students. And Harry has no clue he's a Horcrux and needs to die because there is no Snape to give him the information. Which essentially means Voldemort wins because he can come back through the piece of his soul in Harry.
Nobody, including the audience, understood who Snape was or what he stood for up until he died. He was an incredibly complex character trapped between trying to help his friends and being unable to leave his position as a Death Eater. I think of almost any character written into the books, Snape suffered a lot more than most of them.
Snape wasn't good or evil. He was gray. As humans none of us are perfect. We all have a bit of light and dark in us. The flaws and imperfections are what make us human. Severus is the embodiment of that humanity. Snape was someone everyone could connect with. You either loved him or you hated him. Considering the fact that years later we are still debating him, I feel like he was exactly what J.K. Rowling wanted him to be.
Whether you believe him to be the Hero or the Villain, you cannot deny that Severus Snape was a masterpiece of a character.
To see Severus' story from beginning to end, check out the following video by kcawesome13
Severus Snape | Important Scenes in Chronological Order Youtube