I'm trying to give some closure to all the fics I never finished. Here's the ending I planned for "Yin and Yang." I hope no one is too disappointed. Thank you to everyone who read it.
At the story's climax, a group of Cons attacks the Autobots, including the Con that carved up First Aid's face. When confronted with him, First Aid breaks down in a panic attack and Knockout has to save him. First Aid eventually recovers enough to help KO at a dire moment.
After the incident, KO repairs First Aid. He convinces First Aid to remove his visor and mask, revealing the scars-drawings that would be beautiful if they weren't carved into flesh. Realizing that First Aid is not the naïve and sheltered innocent he'd thought at first makes KO much more tolerant of him, He offers to help First Aid get over his PTSD.
"I don't have a degree in psychotherapy—but I have high-grade and functioning audials, and those can amount to nearly the same thing."
First Aid couldn't hold back a smile. He knew several therapists who would throw a conniption fit if they heard that. But none of them were here right now—and Knockout was willing to listen. "That…sounds nice, actually."
Story ends with Knockout talking to the little memorial he made for Breakdown—he does this regularly as a sort of therapy. He figures it's perfectly healthy as long as the memorial isn't talking back. He talks about how First Aid is progressing, and how he's amazed he actually considers the medic a friend now.
"I'm not replacing you," Knockout said softly. "I don't think I could even if I wanted to. All the experiences we shared—the mines, the gladiator pits, the battles we fought together—those can't be duplicated. You can't replace a best friend. But you can make new ones. I hope you're making lots of new friends, wherever you are. Maybe someday when we're all in the Allspark, we can party together."