Ever since we heard the prophecy at the end of Order of the Phoenix, one of the main things I've worried about is how Harry was going to defeat Voldemort without resorting to evil's methods. We've known, of course, that Dumbledore believed that the only way Harry could win was through the power of love, and that turned out to be blessedly true. But I still wondered how it would happen. How would JK Rowling show us a decisive victory over Voldemort (and make certain we knew he was dead) without depicting Harry as a kind of murderer?
I think she succeeded brilliantly in showing us deep qualities of mercy in Harry. And one of the master-strokes is the way Harry uses the "Expelliarmus" spell at the very end, instead of the "Avada Kedavra."
Let's lay aside (for now, though I'd like to come back to it sometime) the troubling facts that at different points in the narrative, Harry casts the other two curses that have been classified as unforgivables by the ministry. But he never casts an AK, the curse that killed his parents and that should have killed him twice.
One of the things I didn't expect, and which was a fascinating part of Deathly Hallows, was that by the time Harry met Voldemort for the final confrontation, he would be in a place of calmness and strength and power. I think I always imagined the final confrontation as a desperate moment with Harry somewhat cornered, yet protected and helped by love outside (as well as inside) himself. He was certainly helped all through DH, and would never have gotten as far as he did without the help of countless others.
When the final confrontation boils down to just the two of them, however, it's clear Harry has the upper hand. Voldemort has lost all his horcruxes, which we know has left him in a weakened state. He's lost Nagini and most of his other supporters, including Bellatrix. And as Harry unwinds the narrative, for him and for us, we begin to realize that Harry is pretty sure that he also has the upper hand in terms of weapons. He's wielding what looks like a lesser wand, but because the greater wand recognizes Harry as its new master, his spell should be able to defeat Voldemort's.
I hadn't imagined the complexity that Rowling could bring to bear on the whole "Deathly Hallows" subplot, and especially on the wand exchanges. That was brilliant, with that seemingly insignificant little moment on the tower when Draco disarms Dumbledore in Half-Blood Prince being so key. (The only other seemingly "throwaway" moment that might have seemed even more brilliant was the way in which Dumbledore used the golden snitch Harry almost swallowed in his very first Quidditch match six years before.)
So by the time of the final confrontation, Harry is in a place of power: he's the master of the Elder Wand, he has Voldemort cornered, he has done everything he was supposed to do to ensure the other's vulnerability. And what is beautiful is that, standing in that place of power, Harry chooses not to wield it with utter forcefulness, not to vengefully cast at Voldemort what Voldemort cast at him and his parents. He restrains his power. Instead of seeking to kill, he seeks to disarm, a word positively fraught with biblical connotations.
There is even a strange sort of beauty (or if that's not quite the right word, perhaps nobility is better) about the way he casts it. It's not accompanied by a cry of rage or glee. Voldemort "shrieks" his final curse. But although Harry also yells, his yell is depicted in almost prayerful tones: "he too yelled his best hopes to the heavens" (and how marvelous that he is in the Great Hall at the time, with the clear light of sunrise dawning).
Lest we miss the point, JKR gave us that wonderful exchange in the early chapters where the death eaters figure out the true Harry's identity (in the midst of the decoy Harrys) because Harry uses "expelliarmus." It's an unusual move, one that doesn't seem to make a lot of logical sense, but one that's very Harry. He used it in graveyard in Goblet of Fire, he taught it to the DA students in Phoenix. It's becoming his "signature move," and Rowling makes it utterly clear, in the way Harry explains why he chose to use it rather than send the imperiused Shan Stunpike plummeting to his death, that it's a move of mercy and recognized as such by his worst enemies.
Harry shows mercy to Voldemort here, even in the act of ensuring his destruction. He throws the milder, disarming spell versus Voldemort's enraged killing curse (note we've got red versus green again!). Why is Harry ready to show mercy?
I think there are many reasons. Here are just a few:
• Harry has seen what Voldemort "will become." I think this refers to the awful bit of Voldemort's lost soul (is it the piece that was blasted out of Harry?) which is beyond help in the waystation/waiting room/train station between the worlds after death. This is one reason he tries, although unsuccessfully, to remind Voldemort that only real remorse can possibly re-knit his unravelled soul. (Sidenote: Shades of C.S. Lewis' "Weight of Glory" essay here, where Lewis reminds us that everyone we see has an eternal destiny, and that should affect our own actions.)
• Harry has been able to enter into some measure of real empathy with Voldemort. As awful and evil as Voldemort is, he and Harry shared common experiences and deep connections. Let’s not forget that as he was walking toward death, Harry remembered that Hogwarts was home to him, to Voldemort, and to Snape, "all the abandoned boys." Considering the depth of his hatred, once upon a time, for Snape as well as Voldemort, being able to see some of the painful childhood feelings he shared with his enemies was very important for the growth of Harry’s own soul.
• Harry has been trained in righteousness. I think this is the most important point of all. All through his years at Hogwarts, although he did not know it fully (and although we as readers did not know and understand it fully either) Harry’s trials have helped to prepare him for exactly this moment. Albus Dumbledore, his primary mentor, helped train him for what Albus knew would probably very well be a certain death. Albus couldn't prevent that, and I think for a long time (before the "gleam of triumph" and the "flaw in the plan") he thought the best he could do for Harry was to train him for a holy death, a brave and courageous death that might win release for others. That's why he gave Harry so many chances to face evil and temptations and hardships, even as early on as the events in Harry’s first year at Hogwarts in Philosopher’s Stone. Perhaps even as early on as leaving him on the steps at the Dursleys. And we see Harry's progression in mercy all through the series, including what I still think is one of the deepeest emotional/spiritual turning points of the series: when thirteen year old Harry spares the life of Peter Pettigrew, the man who betrayed his parents.
There are many things here I'd like to explore more fully later. For now, I'm just quietly celebrating that when it mattered most, Harry showed mercy. It was not a curse of Harry's that killed Voldemort, but the rebounding of Voldemort's own rage and hatred. Harry aimed to disarm.