This is a prompt for a writing contest on a discord server. For this story, the first two songs describe the two characters' personalities during the situation which the third song (mostly) describes;
-Love of my life: Sideswipe
-Forgive me: female soldier
-Fairy tales: breakup

All three songs are by Serenity.

Note: There's a line that's supposed to have a crossed-out word. It's not hard to find, and it's not a typo.

Cadi Bevan is a soldier who fell for Sideswipe; even after being warned he's not faithful, he cheats — as Sunstreaker puts it — he's a male version of a slut. Until she caught him making out with another female soldier. That was the last straw, and Sideswipe isn't taking the breakup well.
Warning; graphic details of murder-suicide

Cadi's P.O.V.
I thought everything in my life was going great; I have my dream job working in the military. With the Autobots, my family is supportive of everything, even my boyfriend being one of the Autobots. Until that day...

It was a good day, even though Sideswipe and I couldn't spend much time together. We have plans for a date night. I try to have a texting conversation with Sideswipe, but oddly he ignores me. No way he's busy with his work. Probably getting lectured by Prowl.

Walking down the hall towards the cafeteria, I catch Sideswipe making out with another female soldier, Elana Sharp. Anger fills me as I watch that aft.
"You fucking bastard!" I rage as I walk up to him, "so, is this why you ignored my texts all day?!" I hit him so hard that I left a mark before walking away.
"Wait, Cadi!" Sideswipe yells. I hear he's running after me until I reach my room.
"Fuck you, Sideswipe! Go spend time with your new girlfriend; we're through!"
I enter my room and slam the door in his face before sinking down to the floor, letting myself cry.

Sideswipe's P.O.V.
I return to my room, ignoring Elana's texts.
"What did you do?" Sunstreaker asks.
"Is it that obvious?"
"Aside from your voice? Yes."
"I-I fragged up, and Cadi saw it all... we're through..."
"I warned her you're unfaithful. You did this yourself."
Sunstreaker walks out of the room. I play the song I remember Jamie and I listening to. It's funny I'm going from worrying about what Jamie thinks when she listens to songs like this to thinking this song describes the situation.

Love of my life - you've hurt me
You've broken my heart, and now you leave me
Love of my life, can't you see
Bring it back, bring it back
Don't take it away from me, because you don't know
What it means to me.
Love of my life don't leave me
You've taken my love and now desert me
Love of my life, can't you see
Bring it back, bring it back
Don't take it away from me, because you don't know
What it means to me.

"I'm sorry, Cadi," I sob.

Hurry back, hurry back
Please bring it back home to me,
Because you don't know what it means to me -
Love of my life

Cadi's P.O.V.
I hate this feeling; anger and sadness. I feel sick. Should I be disgusted I still love Sideswipe? Even though I know, he won't learn after this. How long before he kisses another girl?
"Cadi? It's me, Sunstreaker."
I let him in; I know he's not here to tell me I should get back together with Sideswipe. I thought he'd tell me he did warn me, but he hugs me.
"I'm not here to suggest we get together as payback either," Sunstreaker assures me.
All he does is hug me as we sit on my bed, and I cry.

don't believe in fairytales
After you anymore
See you standing with another man woman.
I feel like never before
I don't believe in fairytales
Try to stop the dark fall
Fadeaway with an empty soul
The darkness, I will call.

I know what I have to do...

Sideswipe's P.O.V.

I haven't seen Cadi all night or all day the next day. I haven't seen Elana either. Neither of them will answer my calls or texts. I'm about to go to Red Alert's office to ask him to look at the security cameras when I see Cadi walking to the hanger... dragging Elana behind her. She's tied up, and her mouth is duct-taped.
No, Sunstreaker, you didn't...
I text Prime, Red Alert, Prowl, and Lennox as fast as possible — glad I can text all four at once — before running into the hanger.

Cadi already has Elana tied to a chair. She's armed with a knife and a gun.
"Cadi, you don't want to do this."
I walk towards her slowly with my hand on my gun.
"If I can't have you, no one can!"
"I'm sorry, I —."
"It's too late for sorry!"
She begins to cut Elana's throat; Elana's screaming is muffled due to her mouth being taped. I don't know why Cadi doesn't want to hear Elana's screaming.
"Stop, Cadi!" Prime orders.
She repeats what she told me before pulling out her gun, aiming at Elana's head.
Do something, Prime.
Before anyone can move closer to stop her, Cadi pulls the trigger. Blood pours out of Elana's head. Her terrified expression remains.

Please forgive what I've done to you
All my words so hard to say, I'm blue
Tried to find another way than losing the best man
But love is incalculable when there's no time to wait

"Cadi, what are you doing!?" I panic as Cadi points the gun to her head.
"I said if I can't have you, no one can."
"No, Cadi—!"
I'm too late; her body falls into my arms. Blood pours out to the floor, but I can't let go.
"I'm so sorry. I-I truly loved you. I-I..."
There's nothing I can do but cry until I'm forced to let Ratchet take her body. I kiss her one last time before Sunstreaker takes me to our room.

I stand in the shower, hoping the running water will drown out my crying. It's not like Sunstreaker doesn't know I'm crying.
As the song goes, I don't believe in fairytales after you anymore.