@MooseBreath Snape was a villain who obsessed over and fetishised his childhood crush, and was only fighting against Voldemort and the Death Eaters because Harry (who he bullied to excess along with countless other children) had the same eyes as Lily.
I disagree- Snape was probably the best character (despite being the least likeable). He showed tremendous courage. He grew up and fell in love with the girl next door. His school boy nemesis won her heart and he was (understandably) sour. This was combined with some nasty character traits, like being muggleist, and cruel. That said, his redemption, his greatest feature, was his love for lily. Sure he was creepy about it as a younger man, but the second her life was threatened, he, at great personal risk, did everything he could do protect her, and in honour of her and her love, protected her son. He despised Harry for being James' son, but loved and cared for him anyway. Risked his life and eventually gave up his life to protect Harry. His defective character traits make him unlikeable but he is still a good guy.
Her writing (as PP above) isn't that great, but her characters are brilliantly thought out and she wove the whole world in a masterly way, and it is written with a very Christian horizon (which has been subtley and well done) with regards the whole conflict around the fear of death and courage in the face of death.
Snape was villainous, but certainly not a villian- because he loved lily he avoided the worst crime that Voldemort can never avoid (and JK Rowling's theme around the root of evil being the fear of death)- he becomes unafraid of death because he loved lily so much he recognises that it is worse for lily to have died in vain than for him to die, thus his redemption. He is able to act with courage and love despite being tortured by the fact that lily chose James not him, due to his love for lily. Harry represents both his greatest personal loss and also the only possibility of redeeming himself after betraying her (accidentally) to Voldemort.