Arrow, Season 2

Oliver:
I didn't know, Felicity. Five years ago, I was a completely different person. And I had... no idea that something like this was even... possible. I couldn't have imagined. When you and Diggle brought me back to Starling City, I made a vow to myself that I would never let anything like the Undertaking happen again.

Felicity:
What's happening now is not your fault.

Oliver:
Yes, it is. I have failed this city. Yao Fei. Shado. Tommy. My father, my mother. All that I ever wanted to do is honor those people.

Felicity:
You honor the dead by fighting. And you're NOT DONE fighting! Malcolm Merlyn, The Count, The Clock King, the Triad - everyone who was trying to hurt this city, you stopped them. And you will stop Slade.

Oliver:
I don't know how.

Felicity:
Neither do I. But I do know two things: You are not alone. And I believe in you.