I like what you wrote but it was alot on the short side. Personally, I look at something like this and see the other possibilities. You cover the what if's pretty good in this but you also have to look at the pain on his side and the regret. He lost his best friend on October 31st, 1981 in the physical form because he never was able to make amends with her and lost her years prior do to his stupidity in choices and with uttering a two syllable word, mudblood.
Further regret is that with the uttering of that one word he had the power to make an honest apology and fix things but did not due to either his pride or personal arrogance.
Last, he had to deal with the unhealed wounds of what that one word did every day of his life, and had the constant reminder of her emerald green eyes staring at him from the younger face of his enemy.
William Butler Yeats wrote, "Hell is the place of those who have denied, They find there what they planted and what dug, A Lake of space and a wood of nothing and wander there, and drift, wailing for substance," which screams of regrets and of what if's.