Scars Can Heal

You know... in the beginning of my journey, I probably would've been a bullcharging idiot that tries to smash through problems head-on. But fighting an unstoppable force like Amon, I've realized that bruteforcing doesn't always work. I've even learned how it can hurt my friends.
...
I was frustrated and confused at first and hated me for my own uselessness, but airbending set me on the right track. I slowly realized the avatar is not supposed to be a destroyer. He restores balance to the world. He is the healer of this planet.

In an alternate universe, Korra actually has character development and once she completes it and finds forgiveness for Amon, she unlocks the avatar state. Amon, captured by benders and non-benders (who think Amon has become the arrogant, violent monster he tried to fight) expected something wildly different when he saw a hand approach his forehead like many of his victims before.