The Flash, Season 3

[While treating Iris with her cold powers, Caitlin begins to revert to Killer Frost.]

Caitlin:
Just a little bit longer and she's dead. How's that for changing the future?

Julian:
I know who you are, Caitlin. You do not want to do this.

Caitlin:
This is who I am. You said it, it's time for me to take responsibility for my actions. Time for me to own who I really am.

Julian:
Who you are is Caitlin Snow. I know first hand the battle going on inside of you. I know what it feels like. When it happened to me, I lost. All right? I was weak. And I let it win. And I did... I did horrible things to a lot of good people, and you don't have to do that. You're not gonna do that. You're stronger than that, Caitlin, you're far stronger than I am. You're one of the strongest people I've ever known. You can win this fight. [puts a gentle hand on her arm, speaks softly] Iris needs your help now.

[Caitlin's eyes turn normal again as she regains control, and she resumes helping Iris.]