Oliver and Felicity in “Unfinished Business”

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.