Smallville, Season 10

Clark Kent:
I don't know if you're a ghost from my past or the darkness Jor-El that warned me about, but this will come to an end, just like I did the last time.

Brainiac 5:
I hope so for your sake.

Clark Kent:
My sake? You sent the person I love away. You tried to destroy Chloe, you tried to destroy the world.

Brainiac 5:
And you saved me from all of that, Kal-El. I have come back to do the same for you. (shows wearing Legion ring)

Clark Kent:
The Legion. You're from the future. What'd you do to them?

Brainiac 5:
I joined them. In the 31st century, I'm known as Brainiac 5. The ring, time travel - all my creatons. I brought the Legion into a new realm of heroism.

Clark Kent:
I helped them destroy you.

Brainiac 5:
No. They helped you cure me. The problem is Kal-El, you and I aren't very different. We were both created in one way or another by Jor-El, both intended to save civilizations, to bring peace to a brutal world. But neither was immune to corruption to darkness.

Clark Kent:
What does that mean? All of sudden everyone's telling me that I have darkness within me. I don't understand what it is or how I'm suppose to change it. You destroyed cities. I may not make the right decisions, but at least I'm trying to save people.

Brainiac 5:
Then let me show you, Kal-El. We can't always see it in ourselves, my corruption started with a nanobyte - smaller than the eye can see. But that's all it took.