Younger/teenage me was quite ready to forgive Snape for all he did since he helped in executing Dumbledore's plan to stop Voldemort; he saved Harry from Quirrell. However, rereading the books as a tad more mature adult, I would say Snape certainly does not deserve redemption. He was such a bully to students, especially to Neville and Harry; he belittled Hermione for being brilliant etc. That sort of behaviour disgusts me. No matter what he may have been through at the hands of Sirius and James, he could have made better choices to not follow in their footsteps with another generation of witches and wizards. Snape of all people should have known what that bullying felt like and he failed miserably by being a good human and treating others kindly.