Professor Snape's very last line reveals more about the Harry Potter character than you might think. Hogwarts School of Witchcraft and Wizardry is full of fascinating faculty members, but none more so than Professor Severus Snape, expertly played in live-action by the late Alan Rickman. For the best part of six books (and seven movies), Snape treats Harry like leftover Flobberworm Mucus. Still, a rough time in the classroom was nothing compared to Snape executing Albus Dumbledore and joining Lord Voldemort in The Half-Blood Prince, seemingly confirming Harry's long-held suspicion that the ex-Death Eater was a snake all along.
The truth was far more tragic. As a young Hogwarts student himself, Severus knew Harry's future parents, James Potter and Lily Evans. Brash and overconfident, James would torment the timid Severus, leaving Lily, a kind and charitable soul, to pick up the pieces. Snape fell deeply in love with his guardian angel, and was left distraught when Lily chose James instead. Though the potion master served as a fully-fledged Death Eater during Voldemort's first reign of terror, rejoining the Pale One's evil fan club was merely a ruse to bring the Dark Lord down from the inside.
This backstory forces a reexamination of Snape's actions towards Harry Potter - especially in light of the professor's tear-jerking final line. Clapping eyes on James and Lily's son as he slowly succumbs to death, Alan Rickman's Snape remarks on how Harry has his "mother's eyes." Finally, this explains why the infamously prickly prof always treated Harry with such venom. Constantly seeing Lily's eyes staring out from among the desks reminded Severus Snape of the one true love that left him in the friendzone to run off with Hogwarts' champion bully. That bubbling resentment surely influenced Snape's snarky attitude toward Harry during potions classes.
But Snape's final "you have your mother's eyes" line also reveals a deeper layer to his relationship with 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. Naturally, He Who Shall Not Be Named wanted these newborns dead, and the resulting battle in the Potter household ended with Lily's sacrifice. Had Snape kept his thin mouth shut, Voldemort never would've targeted Harry, and Lily would still be alive.
Whenever Harry's eyes, eerily similar to his mother's, glared into Snape's from across the classroom, any anger over romantic rejection would've quickly been replaced by immense guilt, as the professor remembered how he was responsible for those eyes being extinguished. Some might question why Snape didn't acknowledge this sooner, rather than treating Harry awfully for 6 years, but only with a sacrifice of his own could the professor truly redeem himself for Lily's death. Before his demise in Deathly Hallows, Snape likely viewed Lily's presence in Harry's eyes as a punishment, but after atoning with his life, he could finally look through those iconic round spectacles and see the woman he loved one final time.
Arguably the most nuanced character in all of Harry Potter, Snape deserved a fitting farewell, and it's difficult to think of a better last line than "you have your mother's eyes." The emotional admission works on numerous levels - it's an explanation, an apology, and a declaration of love - but most of all it's the release of a long-held guilt.