The Legend of Korra, Season 2

Vaatu:
The Harmonic Convergence is about to begin! The Era of Raava is over!

[As the Harmonic Convergence begins, Wan fuses his soul to Raava's spirit, becoming the first Avatar]

Raava:
We are bonded forever.

[Entering the Avatar State, Wan makes quick work of Vaatu, trapping him inside an elemental sphere and imprisoning him within the Tree of Time]

Wan:
This is your prison now, and I will close the portals so no human will ever be able to physically enter the Spirit World and release you.

Wan:
The spirits must stop fighting with humans and return to their home in the Spirit World. I will teach men to respect the spirits so that balance will be maintained. I will be the bridge between our two worlds.

Lion Turtle:
The world is entering a new age. Our time protecting mankind is over. We will no longer give humans the power of the elements.

Wan:
Different groups of people must learn to live together. This is my mission: to use Raava's light spirit to guide the world toward peace.

[At the end of his life, and elderly Wan is lying alone on an abandoned battlefied and has one last conversation with Raava]

Wan:
I'm sorry, Raava. I failed to bring peace. Even with Vaatu locked away, darkness still surrounds Humanity. There wasn't enough time.

Raava:
Don't worry, we will be together for all of your lifetimes, and we will never give up. [Wan dies, and a glowing wisp leaves his mouth. The screen fades to white and a baby is heard crying.]

[Cut back to Korra in the present day. Her eyes glow white as she briefly enters the Avatar State and wakes up.]

Korra:
I remember.

Fire Sage:
Do you know who you are?

Korra:
My name is Korra. I'm the Avatar.