Treblaine said:
How does Harry's exceptional love for his friends help vanquish Voldemort than if he had an entirely functional relationship with his companions? Neville killed the final Horcrux and he had an impersonal relationship with Harry.
Harry's love for his friends is what drives him. When he's facing Voldemort in battle, he's able to hold his own against a vastly superior wizard because he fights for people he cares about, and isn't afraid of dying to protect them. Rowling establishes those kinds of emotions as having power.
As for Neville, he was touched more by Harry's goodness than you think. It's barely touched on in the movies, but the books has Neville joining the Defense Association, gaining friends and confidence from their support. He and Harry meet in the hospital in The Order of the Phoenix, when Neville is visiting his mind-broken parents, and the two make a personal vow, as "orphans" of Voldemort and his evil, to make their parents proud. That strength drives Neville to hold his own against a Snape-run Hogwarts and, when he sees Harry has sacrificed all against Voldemort, he finds the courage to break Voldemort's paralysis, draw Griffyndor's sword from the Sorting Hat, and slay Nagini.
Harry survived as a baby because his mother acted as a human shield... magically. Somehow this Killing Curse killed both her AND reversed it back on Voldemort to kill him, and the final part of his Horcrux go into Harry. Actually, this sacrifice-spell makes the killing-curse a hugely impractical mode of killing. Of all the ways you could kill someone, be it with a spear, crossbow, gun, flamethrower, chainsaw... what could they possibly do to make such an attack kill themselves but ALSO kill the dealer? Short of a suicide-bomber's vest which kills everyone within a 20 meter radius.
The "somehow" you mention is love. Lily was willing to die defending her son, and when Voldemort killed her, her sacrifice created a powerful ward on Harry. When Voldemort turned his killing curse on Harry, that ward repelled the magic that destroyed Voldemort's body. Even Voldemort mentions this, calling it "old magic" that he didn't consider when he tried to kill Harry, and goes so far to use Harry's blood to rebuild his new body thinking that it would circumvent the protection her love provided (and it did, to a small extent).
And killing curse is apparently the only spell which is SPECIFICALLY designed to kill. The question shouldn't be why don't they shoot Voldemort but rather why doesn't Voldemort use a gun himself!?!? Guns WITH magic would be a HIGHLY effective combination. Like combining laser guidance systems with high-explosive air-dropped bombs, to give the Laser Guided Bomb that can deliver several tons of high explosives right through a ventilation shaft... or some "Force" guide a proton torpedo down a thermal exhaust port:
Magic sometimes has an odd effect on technology built during or after the Industrial Revolution. This is most obvious when Arthur Weasley's car spontaneously "goes feral" and drives itself off into the woods, where it presumably remained.
For that matter... why would Voldemort, an insane wizard-supremacist, even consider touching a "filthy muggle" artifact? They very idea would make his skin crawl, and to borrow from your own example "the ability to destroy a planet is insignificant, next to the power of the Force."
All the magic in Harry Potter just seems so arbitrary and open to abuse it's meaningless even within a work of fiction. It's not like a new set of rules, it's rules change all the time.
Yes, they do. I believe Rowling herself admitted as much. Magic exists outside of physical laws, so it stands to reason that it can be easily convoluted.
And the Elder Wand thing. That's not love, that's providence. Or in this case where we know it is a book, plot contrivance. JK Rowling conveniently made the random events of wands exchanging hands means the Elder Wand was Harry's and then introduce the element of obedience in wands so refuse to cast a Killing Curse on the owner... even though it did so minutes earlier, where Harry was again saved by convenience beyond his plan or will, did the wand "know" that?
In the Elder Wand's case it's an example of Voldemort's evil destroying himself. He seeks it out, believing it would prove more powerful than Harry's wand (since his own wand is it's "equal" and when he used Malfoy's wand, it blew up), never imagining that it was Harry's mindset: his courage and willingness to fight and die for his friends, that was making Harry the "better man" in this duels. Voldemort can't even conceive of love so he just kept seeking "stronger" wands, believing that the Elder Wand, as the strongest, would turn the tied.
I admit, how it switched hands is very convoluted, but I would imagine it understood what was happening as Voldemort cast the killing curse on Harry: first it sensed its true target was the fragment of Voldemort's soul inside Harry, and second it knew it was being used against its master. Ollivander suggests that wands can choose their allegiances, and the wand doubtless felt that Harry was the more worthy wielder.
I won't say it's not convoluted, but this is how the books play out.
This has nothing to do with love and compassion. This has to do with Harry stealing Draco's wand after he betrayed Dumbledor and Voldemort not understanding the rules of magic that Rowling is clearly making up as she goes along. So larceny on top of betrayal depending on ignorance...
Larceny, betrayal, and ignorance seem to have a lot to do with the absence of love, however, don't they? Voldemort stole, Voldemort betrayed, Voldemort refused to consider the power of love in Harry, and it cost him dearly.
PS: first you say Voldemort is motivated to kill Harry by hatred. Then suddenly you say he is motivated by practicality, that he thinks he must do it to survive. Which is it? Is it both? It's not unreasonable to hate someone that is going to cost you your life, even if a delusional opinion that makes him insane, not evil. Insane to kill a baby at a time when it clearly posed no threat nor ability to even indicate threat.
Obviously he set out to kill Harry as a matter of practicality: we can't have a boy destined to destroy me lurking about. He read his Evil Overlord List. But as Voldemort's efforts continued to fail and backfire, it quickly turned to hate, with a little fear and desperation mixed in.
Think of it this way: you're playing a multi-player game, and someone kills you. Fair enough. But then you spawn in, and he kills you again. Now you've got a grudge to settle. You seek him out, hoping to get even, but in the ensuing battle he kills you a THIRD time. You start actively hunting him, intent to make him pay. You start making mistakes; maybe you let your teammates die so you can chase this guy around the map, maybe you leave yourself open to being killed by your new enemy's own teammates. But it goes on and on and you can't land a single kill, and even worse, he kills you a few more times. Tell me you wouldn't start getting pissed off as this point.