Character Analysis
We know it's not nice to enjoy other people's suffering, but there is something really satisfying about watching this sadistic, evil, psychotic wizard get what's coming to him.
Finally.
Yup, that's right: Voldemort finally goes down in this film. And the best part? He contributes to his own downfall. Let's take a look at how he helped banish his evil self from the world, once and for all.
Wand Magic
But let's begin at the beginning.
When the film starts, he has just gotten his hands on the Elder Wand, which is supposedly the most powerful wand in the world. Ever. Even Ollivander, the famous wand maker, tells Harry that if Voldemort is in possession of the wand, everyone else is in big trouble:
OLLIVANDER: He's after you, Mr. Potter. If it's true, what you say, that he has the Elder Wand, I'm afraid you really don't stand a chance.
So, yeah, with multiple Horcruxes still out there undestroyed, and Voldemort in possession of this super wand, we're not feeling fantastic about Harry's odds of defeating the Dark Lord.
Horcrux Horrors
Luckily, Harry jumps right back on the Horcrux hunting horse (say that five times fast) and starts knocking out Horcruxes one by one. First, he guesses accurately that Bellatrix has a Horcrux in her vault, so he goes to steal that one—which tips Voldemort off about Harry's mission.
Despite now being aware of Harry's strategy for defeating him, Voldemort isn't super effective at stopping it. In fact, he even gives Harry a clue to here the location of the next Horcrux when a fit of anger opens up that connection between his mind and Harry's.
After "seeing" Voldemort realize Harry's plans, Harry notices that his thoughts turn immediately to Hogwarts. So, Harry goes to Hogwarts, finds the next Horcrux (Rowena Ravenclaw's diadem), and boom: that's yet another step closer to Voldemort's destruction.
When Voldemort realizes the diadem has been destroyed, he knows he has to protect his last (known) Horcrux: his snake, Nagini:
VOLDEMORT: Come, Nagini, I need to keep you safe.
Unfortunately for Voldemort, Harry is privy to that moment because, once again, Voldemort's anger has opened up that connection between their minds:
HARRY: It's the snake. She's the last one. It's the last Horcrux.
So, Harry sets out to destroy the snake and (fingers crossed) destroy Voldemort soon after.
Only one problem, though: the snake isn't actually the last Horcrux. Harry is. Dumbledore explained how this happened to Snape, and we see the convo via Dumbledore's Pensieve:
DUMBLEDORE: On the night Lord Voldemort went to Godric's Hollow to kill Harry, and Lily Potter cast herself between them, the curse rebounded. When that happened, a part of Voldemort's soul latched itself onto the only living thing it could find: Harry himself. There's a reason Harry can speak with snakes. There's a reason he can look into Lord Voldemort's mind. A part of Voldemort lives inside him.
So, yeah, if Voldemort is to be destroyed, Harry needs to be destroyed, too.
Love Strikes Again
Or: make that temporarily destroyed. Harry tries in good faith to let Voldemort kill him so that someone else (presumably) can finally finish the Dark Lord off later. Voldemort, unaware that Harry is a Horcrux, is beyond thrilled when Harry gives himself up:
VOLDEMORT: Harry Potter: the "Boy Who Lived." Come to die. Avada Kedavra!
However, Harry doesn't die (and for those keeping score at home, that makes Voldemort 0/2 in using the Killing Curse directly on Harry). Instead, only the Horcrux living on/in Harry dies, and Harry lives to fight again. And this time, he duels with Voldemort and wins, which results in Voldemort disintegrating into thin air.
And that, folks, is the end of the Dark Lord. For good, this time.
…We hope.