Little more needs to be said about Neville’s heroism in book seven, both in leading the resistance at Hogwarts and in carrying out Harry’s instructions to kill the snake Nagini even when all seems lost. Neville’s transformation from hapless doofus to stouthearted wizard is one of the notable (and well-noted) examples of personal growth in the series. He’s come along way since his first line: “Gran, I’ve lost my toad again.”
But the courage he displays in the last few books shouldn’t be a complete surprise. Recall that at the end of book one, it’s Neville who tries to stop Harry, Ron, and Hermione from sneaking out to look for the Sorcerer’s (or Philosopher’s, in the original) Stone. Hermione has to hit him with a body-bind curse. Later, when Dumbledore is awarding points to the three for their cleverness and courage in searching for the Stone, he concludes:
“There are all kinds of courage,” said Dumbledore, smiling. “It takes a great deal of bravery to stand up to our enemies, but just as much to stand up to our friends. I therefore award ten points to Mr. Neville Longbottom.”
Those ten points put Gryffindor over the top to win the House Cup. Although the Sorting Hat takes “a long time to decide with Neville,” it finally chooses Gryffindor. Since Neville magically pulls the sword of Gryffindor out of the Hat at the end of book seven, it would seem that the Hat knew what it was doing.
And oh yes. The curse of Voldemort’s that Neville escapes from as he kills the snake? A body-bind curse.