Whatever they have planned for me on the 11th, I just hope it doesn't hurt. Comment if you want, I don't care anymore. I'm so sorry for everything guys. I'm so fucking sorry.
Noah confessing that he was the one who killed Kat.
I was being controlled somehow, and, I—I killed her. [sobs] I don't know how they made me do it, but, they, they made me do it. In cold blood. [laughs] Like it was nothing. Like I'm some kind of goddamn puppet. That blood on my shirt? In the video? That was Kat's. She must have put up some fight.
"See you soon, Milo."God.
Firebrand interrupting the Observer and saving Noah during Interception. The sheer relief when you realize that after all this time someone cares about Noah and is stepping in to ensure his survival is enough to bring on the waterworks.
"The Live Stream Incident". Five minutes before midnight, Noah has a breakdown and finally admits that for all his posturing, he is terrified to die.
Noah: (tearful) I'm really fucking scared, guys. I don't wanna die. (begins to cry) I want- I have my whole life ahead of me! I want to live! I don't care about any of this supernatural bullshit anymore. I want to...I just want to live!
Noah's final words to Firebrand, spoken in private after he ends the stream:
Noah: (tearing up) Firebrand...me... Thank you. Thank you. (Turns off camera as he begins to sob.)
DEUS EX MACHINA gives us a hint at how Firebrand broke free of the Collective: it involves some kind of deal with HABIT. It is heart-ripping to imagine a situation so dire that making that kind of Deal with the Devil is the better option.
Furthermore, Firebrand explains that he's had the journal the Collective are after ever since he broke free from their control. The journal is what has been protecting them from their wrath, and possibly from being controlled again. He intends to give the journal to Noah, therefore sacrificing himself, "For you, for us, for all of us." As he says this last part, it shows various people in a city, meaning he's giving himself up to save humanity.
In Obituary, there is the way that Noah talks about inevitably becoming Firebrand, and how the video reveals that Mr. Scars is Milo and he killed Mary.
Milo's letter to Noah in Extraordinary Circumstances.
May this case full of my old belongings somehow aid you in fighting whatever is plaguing us. Unfortunately, by the time you receive this, I'll surely be dead. I am sorry that I cannot explain more, because I think it may jeopardize my life under the recent extraordinary circumstances of my current existence, but I think you'll be able to figure it out in the end. I trust, you, old friend.
This is especially poignant considering that until now, Noah has harbored a lot of guilt over Milo's death — both for not being there when Milo needed him, and for being unable to avenge his death. The note effectively shows that despite everything, not only does Milo not blame Noah for his current circumstances, but he still trusts him implicitly — and that despite no longer being human, he still loves him like a brother.
It also makes the previous entry a bit more heartrending: that was Milo's hand pressed against the glass. His own cousin — the living, human version he'd known in childhood, the one who was once like a brother to him — was right there on the other side of the glass, just a few feet away. And he couldn't even say a word.
Mr. Scars kills Mary Asher in Milo's Tape. The sad part? Mr. Scars is Milo, and he killed his own mother. Observer, you DICK!
Mr. Scars/Milo: It still hurts.
Even worse, it's hinted that Milo literally had no control over his actions in that moment, any more than Noah did when he killed Kat. After he realizes what he's done, he breaks downcompletely.
Mary's reaction to seeing Milo alive. She may have been a crazy, selfish bitch, but he was still her son.
"Milo! My baby!"
On the flipside, however, there's the heartbreaking revelation that Mary only had Milo so she could sacrifice him to the Collective, in the vain hope that she could "buy off" the Administrator and end his malign influence on their family. Small wonder her Collective title is "The Selfish".
While Evan/HABIT threatens Noah on the bridge in "Bridge to Nowhere," he asks him, "So, what are we gonna do, Noah? Are we gonna fight, or are we gonna die screaming?". Noah simply responds, "I just wanna go home," like a child would if they were in a situation like that. It's a tad subtle, but it's so sad considering how scared Noah is.