Patriot's suicide letter is a paper note in Fallout 4.
Location
It is given to the Sole Survivor by Desdemona after completion of The Nuclear Option (Railroad), when they witness Patriot's funeral.
Transcript
You betrayed me. ME! After all I did for you. I trusted you. I risked everything to help synths. To help you. And this? This is how you repay me?
My father is dead. Everyone I loved and cared about was vaporized or lost in this barren irradiated shithole. Because of you.
I used to feel sorry for you. You lost your son. You missed out on every moment of his life. Now, I see it's only what you deserved.
I cannot live with myself. Due to my stupid trust in you I've destroyed humanity's best hope for the future. If there's any fairness in the world you'll never get a good night's sleep in what remains of your hopefully short, miserable life.
- Liam