The genius of the series lies in how Voldemord's character is developed at the same time as Harry's. What makes Harry better is not his magical powers, but the presence of 'muggle emotions'- mainly the ability to feel remorse and loyalty.

Voldemort becomes increasingly 'inhumane' during the book. We are bought closer to him. In Book 1, he is a far-off figure that we never glimpse. In 2, we see snatches of his childhood. There is a series of progressions where Harry begins to infiltrate his inner circle (Bellatrix in the Battle of Hogwarts). As he wins them all, he gets to meet V in the last book.

In each book, we see a layer of 'muggle-ness' being stripped away from V. By the end, the despot has become a paper thin caricature, searching for the Elder wand, the invisibility cloak, and the resurrection stone. He basically wants power, immortality, and control over his 'visibility' (in the metaphorical and literal sense).

Harry's 'muggle-qualities' both weaken and strength him. He cannot cast the 'torture' spell on the death eaters because, as Bellatrix says, he can 'feel only anger, but not pure hate.' Dumbledore in the first book makes a rather off-hand statement that V's inability to feel love is his weakness.

Essentially, the dramatic moment in the novel happens when Harry beats V in a duel in the final book. Harry begs V to feel remorse to save his soul, but V does not react- partly because he is unable to as he has stripped away his human qualities throughout the novel.

The sentimental scene of Harry placing the wand in Dumbledore's grave, and of him naming his child after Snape, is further example of how his character has peaked in self-awareness, mercy, and love for others.

In a world where the best wizards are those who can perform the best spells and unleash the most fear, Harry shows the need for 'muggle' feelings in a culture which does not encourage it. Characters who feel affection previously die in horrible manners- like Black, and Harry's parents.

However, Harry shows not just love, but mercy. Rowling is basically saying that the perfect leader ought to combine the lofty (his mastery at quidditch, his natural flair for 'Defence against the dark arts') with the humane and humble.