By telling the Dark Lord the prophecy, he unknowingly made Lily Potter a target for Voldemort which eventually led to her death. Snape had loved Lily since they were both 9 years old and playing a part in her demise greatly troubled him.
It was Snape that persuaded Voldemort to give Lily a chance to save herself. He also protected Harry during his time at school (however reluctantly). He risked his life constantly as a double agent. He was the one who was in on Dumbledore's plan for Harry.
More than evoking memories of unrequited love, seeing Lily in Harry's eyes would've stirred feelings of guilt within Severus, since it was he who, albeit indirectly, caused her death. As a Death Eater, Snape informed Voldemort of Professor Trelawney's prophecy, which foretold his defeat at the hands of a fated child.
Voldemort had no idea Snape had loved Lily (he was told the latter desired her in a sexual, non romantic way) until Harry told him, hence the wild denial. The evidence for Snape's continued love, his doe Patronus, was known only to Dumbledore.
When Snape heard the prophecy and pleaded with Voldemort to spare Lily's life, he may have inadvertently caused his downfall. While we know Voldemort killed Lily, he did give her a choice. If she stepped aside and allowed him to murder Harry, he would spare her. Lily refused and sacrificed herself to save her son.
Snape's obsessive love for Lily fed his equally obsessive hatred for James, and meant he would stop at nothing ' even arranging the murder of her child ' to possess Lily.
A Professor at Hogwarts School of Witchcraft and Wizardry, Snape is hostile to Harry due to his resemblance to his father James Potter, who bullied Snape during their time together at Hogwarts. As the series progresses, Snape's character becomes more layered and enigmatic.
To be fair, James would (and did) willingly die for Lily too. But Snape loved Lily so much that he was willing to die just to avenge her. He would die just for the memory of her.
12. Snape's Last Words. In the [Deathly Hallows] book, Snape's dying words to Harry were "Look at me". Right then we did not realize the significance of his words but in the very next chapter when Harry goes through Snape's memories in the Pensieve, he comes to know how much Snape loved Lily.
Bellatrix Lestrange was in constant competition with Severus Snape for Voldemort's attention. She was jealous of his magical potential and never trusted him.
We can therefore presumably safely conclude that Lily was not noticeably pregnant at the time she died.
Her leaving Snape wasn't a sign of her being a bad friend but rather that their interests no longer clashed as he was studying something that Lily despised. They just grew apart over time, and that was no fault of Lily's.
Towards the end of The Deathly Hallows, we learn Snape apologised later on. Unsurprisingly, Lily didn't forgive him and severed their friendship permanently.
It's a word that gained so much more clarity and tragedy after Harry Potter and the Deathly Hallows revealed that the nefarious Professor Severus Snape was actually serving a nobler cause: protecting Harry from Voldemort out of love for Snape's childhood friend Lily Evans.
He is also revealed to be a double agent for Albus Dumbledore and the Order of the Phoenix. But many people forget that he also invented a number of spells. In the Harry Potter movies, Snape came up with the Sectumsempra curse when he was a student at Hogwarts, and it's known to cause painful lacerations on the target.
Snape's unrequited love for Lily lead to his greatest fear coming true, a fact that wasn't revealed until The Deathly Hallows. Harry Potter's presence is a constant reminder that he didn't do enough to protect her.
All this implies that James Potter and his friends did have the tendency to bully people for fun or “just because they can”. In fact, James outright tells Lily that he's bullying Severus Snape because of the “fact that he exists, if you know what I mean”.
Later, Snape tries to apologize for calling Lily a Mudblood, but she's not interested; she ends their friendship due to his association with Death Eaters. Seventh Year: James becomes Head Boy and seems nice enough now for Lily to start dating him.
Neville Professor Snape Neville fears Professor Snape who treats him rudely with sarcastic comments. Neville seems afraid of this harsh treatment that makes him feel inferior constantly. Parvati Blood-stained, bandaged mummy Parvati is afraid of something that is scary to her, possibly because it can harm her.
He was cruel to many students, but especially toward Neville Longbottom. It was no fault of Neville's but was instead because of Snape's love for Lily. Neville was almost the Chosen One, and the fact that he wasn't broke Snape's heart to look at him, which caused Snape to lash out cruelly at an innocent child.
Snape loved Lily deeply: through their years at Hogwarts; through her marriage to another wizard, James Potter; through his time as a Death Eater; and long after her murder at the wand of Lord Voldemort.
However, years later, when Harry is 16, Dumbledore sees that Severus' patronus is STILL a doe, like Lily's. Meaning that Snape is STILL deeply in love with her, or at least with her memory. And if you note, it's said more as a statement than as a question - little intonation.
That said, initially Snape saw Harry as James incarnate, and therefor despised him. As their relationship progresses, however, and Snape opens up to who Harry really is (and Harry himself starts to show his best side to Snape), these feelings begin to change.