To answer one of your original questions, the death that keeps hurting the most is Snape’s. I would have hoped for them to come to some understanding while Snape still lived, for Harry to say how sorry he was for his dad’s behavior.
But this way makes it more tragic, and sadder. Harry barely gets there in time to see him die so ignominiously, having no idea what it means. But Snape does, and with his last breath, he tells Harry to look at him — so that (we surmise) he can see those eyes, so like Lilly’s eyes, that he’s dying for.
So bitterly sad.
I think Snape’s death is sad. But at the same time it’s full of redemption. He knows, as well as Harry that he ~must~ die for Voldemort to be defeated.
He also knows that by giving Harry his memory, Harry will understand.
And I think, as shown by the portrait’s of the Headmasters (discussed upthread), Snape knows the outcome and he would have heard what Harry said to Voldemort.
Wasn’t Snape the one who alerted the Order at the end of OoTP. How is it that no one else recognized his Patronus? Sirius would have had a field day with that one.
Snape is definitely the one whose death seemed the emptiest... no particular closing out there, just the knowledge that he had to die. The only part I’m sorry about was that he died thinking it was all for nothing and that Lily’s son was soon to die.
I don’t think Harry needed to apologize for his father’s actions. Harry is Harry and James was James, and I do think that most of James and Snape’s rivalry was over Lily. And most of that was Snape’s doing, I believe. I think he always felt deep down that he wasn’t good enough for Lily, it seems the sort of thing an abused child would think. And then his actions kept pushing her away. Like on some level he wanted her away from him, felt he couldn’t make her happy and James - who was everything Snape wanted to be - could.
But in the end neither man’s love was enough to save her. Her love was what ultimately saved everything, her love for Harry and the friendly shining love that young Snape saw in her from childhood influenced him to do the rest.
Presumably, her love made James grow up into a better person than he was when we saw him at 15. Her love made Snape realize what he was doing. And I think Petunia’s memory of Lily’s love is what made her take in Harry in the first place.