Supergirl, Season 4

J'onn:
You betrayed Supergirl tonight. You betrayed me and your promise to Fiona. No vengeance is worth your soul!

Manchester:
What soul, old man?

J'onn:
I saw the love you had for Fiona, how you fought for her. I also know what you're gonna do, and I can't let you kill a man, even if that man is Agent Liberty. Once you cross that line, Manchester, there is no going back.

Manchester:
You have no idea what lines I've already crossed. [points at J'onn's chest] See that there? That's your heart, beating. Mine is dead. And every time I close my eyes, I wait to hear Fi's voice. There's nothing, just silence. I'm empty, man.

J'onn:
That is not true!

Manchester:
You want to know the truth? [places J'onn's hand on his head and attaches an item to J'onn's chest] Look.

J'onn:
[Sees flashbacks of the people Manchester tortured and killed recently] Why won't it stop?

Manchester:
That's an empathy amplifier. It was created to use against empaths. Don't move around, keep everything in. If I can't escape this pain, neither can you. You shouldn't have believed in me.