Harry Potter and the Deathly Hallows
How we cite our quotes:
"Is it love again?" said Voldemort, his snake's face jeering. "Dumbledore's favorite solution, love, which he claimed conquered death, though love did not stop him falling from the tower and breaking like an old waxwork? Love, which did not prevent me from stamping out your Mudblood mother like a cockroach, Potter – and nobody seems to love you enough to run forward this time and take my curse. So what will stop you from dying now when I strike?" (36.102)
After all these years, Voldemort still hasn't learned his lesson – love does matter, and it is a kind of power he'll never be able to master. Love as a motivation is what has undone him; we've seen it in everyone who's betrayed the Dark Lord, like Snape and Narcissa; people can't help but love, and it's the most powerful force in the world.