Snape was born to Eileen Prince, a witch, and Tobias Snape, a Muggle, making him a half-blood (hence the name, "Half-Blood Prince"). This is rare for a Death Eater, as remarked in the last book, though Voldemort himself also had a Muggle father.
Lily attempted to stop his bullying, addressing James only by his surname and vice versa in this moment. It is implied that such bullying had happened more than once. However, Snape lashed out at her in his humiliation, calling her a "filthy Mudblood."
Even though Snape repeatedly tried to apologize for his mistake afterward, it became clear that it was yet another incident that had done irreparable damage to their friendship.
In the case of Snape. he was Sorted into Slytherin because he was ambitious, leaning towards the Dark Arts, his mother was one, AND he had an anti-Muggle bias, same as Salazar Slytherin himself.
Severus Snape Origins Explained (Childhood to Death)
Why does Snape call himself a prince?
Severus Snape's nickname, the Half-Blood Prince, was a clever description of his half-blood lineage. Snape chose the name as a tribute to his mother and to distance himself from his muggle father, drawing an interesting parallel between this character and Lord Voldemort.
She missed Snape, but she knew she could never forgive him. Snape never stopped trying to make amends. But Lily remained steadfast. She could not, would not, forgive him.
What did Dumbledore mean when he asked Snape Lily?
Then, Dumbledore asked, "After all this time?" I think he was asking whether Snape had this Patronus for the 17 years Lily was dead, whether it changed, whether his loyalty to Lily ever wavered. "Always," Snape responded. Snape has cared for Lily since knowing her.
As the series progresses, it is revealed that his treatment of Harry stems from Snape's bitter rivalry with James when they were in school together. In particular, James and Sirius bullied Snape, which according to Alan Rickman caused the already lonely boy to further "shut himself in".
An interesting fact of note is that despite the ideals that pure-bloods are inherently more powerful wizards, some of the most powerful or particularly adept wizards and witches in the series are in fact either half-blood (such as Lord Voldemort, Albus Dumbledore, Minerva McGonagall, Severus Snape and Harry Potter) or ...
How was Snape a death eater when he was a half-blood?
In a misguided attempt to win back Lily's affections, Snape joined the Death Eaters along with a group of his fellow Slytherins. Severus was made a member of the Slug Club presumably because of his talent in Potion-making.
As much as people romanticize Snape's infatuation with Lily, the fact she did not love him back romantically is ignored. The fact Snape and Lily were only friends, and she only saw it as such, reveals a lot about his refusal to respect her boundaries.
The Snapes were related to the pure-blood Prince family. Sometime before 1960, pure-blood witch Eileen Prince married Muggle Tobias Snape. They had one child, half-blood wizard Severus Snape. The marriage seemed to be unhappy, as they lived in near-destitution, frequently argued, and were neglectful of their son.
In the Harry Potter and the Deathly Hallows movie, Snape showed how much he loved Harry, providing him with his memories and showing that he saw Lily in him, his last words echoing this: "You have your mother's eyes."
Why did Snape stay loyal to Dumbledore after Lily died?
But when Lily's life is directly threatened, he has to make a choice, and he chooses to stand between Voldemort and Lily. To do that, he aligns himself with Voldemort's chief opposition, Dumbledore, and becomes his spy. Even after her death, he remains at Dumbledore's side at Hogwarts and vows to protect her son.
Snape's strained relationship with Lily, who chose James and allowed him and his clique to bully Snape, further pushed him towards the Death Eaters. Despite his love for Lily, the pain from his adolescence couldn't erase the trauma. Snape's redemption came when Lily was murdered by Voldemort.
Notably, Voldemort appeared to be entirely unaware of this split, as he later created a seventh Horcrux in his quest to have six, and continued to target Harry Potter despite him now holding part of Voldemort's own soul.
One with a severe dislike of Lily's former best friend. Let's get into your points one by one, though I would like to say first that I'm not sure if that quote from Lily about James making her sick really matches up with her being the 'submissive one'. - Yes, Lily knows James is a bully. That is why she loathed him.
James was slightly better because he truly did change and he allied with the Order out of basic morality compared to Snape who stayed an all around bitter person. and only allied with the Order out of love for Lily.
Lily didn't agree to date until after Snape had already ruined any chances with Lily by calling her a mudblood and made it clear that his sympathies lay with the death eaters.
For example, Harry Potter is a Half-Blood because his father was a Pure-Blood and his mother was a Muggle-Born. Ironically, Voldemort himself was also a Half-Blood.
He was eventually forced to accept that his father was the Muggle parent, and that his mother was the magical one. It was around this time that Riddle gave himself the alias "Lord Voldemort", to spare himself of the reminder of his "filthy Muggle father".
In his fifth year James saved Severus Snape from a near-fatal prank that Sirius Black played on him, which involved luring Snape to the Shrieking Shack where Remus Lupin was in his werewolf form.
