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Awesome: Dumbledore's Army and the Year of Darkness
Neville has several, but especially when he returns unharmed from the Forest after the werewolf encounter, and when he kills the snake Nagini at the end. All of the main heroes have these moments at some point and most of the minor ones too.
Word of God is that Neville privately considered taking down Fenrir Greyback to be the most badass thing he ever did.