This story was written for the Miraculous Ladybug Holidays Fanfiction Exchange for Reddit user Im-Miss_Understood.
Your prompts were a challenge but I manage to get some inspiration and here it is.

3rd September 2016

"What is given will be taken away," Plagg said his eyes glowing with the shadows "You will not like the sacrifice."

"For Emilie, no price is too high" Gabriel responded,

"Gabriel Agreste," Tikki voice quiet "Have you ever thought about what Emilie would want?"

"She is my wife," Gabriel composed himself "I will not let her go."

With that, Gabriel stabbed the final earring through his ear.

"Emilie," he stroked her cheek, "My Love I'll see you soon,"

Time frozen as Darkness covered Paris as it rearranged itself. Light burst out as the last changes were completed.

In a nearby hospital in a private room Emilie Agreste opened her eyes, and in a side street of Paris Adrien Agreste (covered in scars) collapsed.

October 2016:

"Mrs Agreste! How does it feel to wake up to your son's suicide?"

"Mr Agreste! Do you feel you failed as a parent?"

"Mrs Agreste! Do you blame your husband?"

"Mr Agreste! How did you miss the signs?"

"The Agreste's have no comments at this moment" Nathalie announced nodding as the security pushed against the press.

"Darling I'm sorry you had to deal with that," Gabriel stroked her cheek as the car drove them away, "Someone must have tipped off the press,"

Emilie just leaned against him and let her tears fall. Her baby boy he was so pale and small.

"We need to bring him home Gabriel" She sobbed "He doesn't belong in that place."

"Of course Emilie," Gabriel said, hugging her close, "We'll bring him home."

December 2016:

My fault, My fault, My fault, My fault, My fault, My fault, My fault, My fault,

"Marinette?" Sabine called through the trap door, "Sweetie I know you're in there" she pushed the trap door open.

It was empty.

A chill passed through Sabine "Marinette?" she called a desperate edge entered her voice.

My fault, My fault, My fault, My fault, My fault, My fault, My fault, My fault,

Everyone looked so small Marinette noted. If she just closed her eyes, she could almost feel Chat Noir sitting next to her.

My fault, My fault, My fault, My fault, My fault, My fault, My fault, My fault,

She could almost forget, just like everyone else.

"Princess Justice, I am Hawkmoth,"

She shuddered, "My name is Marinette Dupain-Cheng, I was Ladybug, I was akumatised, Gabriel Agreste was Hawkmoth, he won, nobody remembers, Adrien is in a coma, and he isn't going to wake up. He's not waking up, and it's all—" She burst into tears.

My fault, My fault, My fault, My fault, My fault, My fault, My fault, My fault,

Breathing deeply, legs shaking, she stood up. (I'm sorry Paris, I promised I would save you from evil and-, and I failed") Her tears stopped, and for the first time in three months, she felt calm.

And she let go.

My fault, My fault, My fault, My fault, My fault, My fau-

March 2017

"It's a nice day Marinette," Alya said "Spring really has a way of making things seem-" her hand rose to her mouth as tears started to fall.

"I wish you could see it Girl" she continued "I just don't understand what happened, first Adrien and then you," her voice wavered "Why didn't you come to me? How did I miss this? I-I thought we were a-all go-going to be friends for life,"

She felt Nino's arm come around her, "We all did Alya, whatever happened, whatever lead the both of them down that path," he took a deep breath "We can't blame ourselves for missing the signs,"

Alya nodded wordlessly and leaned further in. They stood there, crying softly as the wind blew past.

The gravestone in front of them was covered in flowers and notes from their classmates.

Marinette Dupain-Cheng

2002 – 2016

You were our Light out of the Darkness

We wish we could have done the same.

June 2017

"Miss Bourgeois,"

"Hello, Chloe,"

"Pollen? But Ladybug said…"

"This is an emergency," Pollen said shortly "Ladybug and Chat Noir have been compromised."

"Miss Bourgeois!" he snapped "It is time for your medication."

"You can fix your own messes too Chloe if you want to,"

"Get away from me!" yelled Chloe "You just want me drugged up so I can't remember"

"This is the last time I can give you the bee miraculous,"

"Miss Bourgeois," he sighed "Must we go over this every time, Ladybug and Chat Noir are not real, you were never a superhero," he chuckled at the last one.

"You-you're wrong," Chloe pleading backing up "You can't be right, I remember, I know I do,"

"I can't let you do that,"

The man sighed and reached into his pocket, Chloe's eyes widened.

"Stay away from me!" she cried out wildly scanning for an escape.

"From what I heard you were nothing but a bully who caused a suicide" he sneered as he stabbed her arm with the needle

"No no, no, that wasn't my fault! It wasn't me, I never want-" she fell silent as her mind clouded over.

A smug look crossed the man's face "Good Girl," he said, patting her head before walking out. "Dumb brat" he muttered, locking the door and moving on to the next room.

3rd September 2017

"Emilie Agreste what is given will be taken," Tikki said eyes glowing "Are you prepared to make that sacrifice?"

"Yes," Emilie replied, "For Adrien's life."

"Is this what Adrien would want?" Plagg interrupted, eyes normal. "To live in the place of another?

"He- He is my son," Emilie choked back tears "I cannot let him go."

Take me back to where it began.

Time seemed to run backwards as Paris rearranged itself.

Go Back!

August 2017

Chloe rolled off her small bed knocking her drawers, "This is Ridiculous, Utterly Ridiculous" she muttered, "I'm not cra-"

Behind the drawers, someone had carved something into the wall.

THIS PLACE IS RIDICULOUS, UTTERLY RIDICULOUS

I'M NOT CRAZY

IS THIS REAL?

AGAIN?

With shaking fingers, Chloe picked up the sharped spoon behind the drawers and pressed it against the wall.

Go Back!

May 2017

Alya's breath caught as Nino opened his mouth "Alya, I-"

("Alya, I can't do this anymore" his voice dropped

"Why, Nino? We're all that's left!" she shouted)

"I know Nino," Alya interrupted tears welling up.

("Alya, I can't be with you" he turned away unable to face her

"Please don't leave like this," she said tearfully "Nino!" she cried as he ran)

Nino's face fell "I'm so sorry Alya," tears spilled from both their faces.

He grabbed her hands gently "Alya, I'm sorry," he whispered, and he let go

"I miss them too Nino!" she sobbed "Don't leave me too!"

Alya pulled him into a hug, "I'm sorry too,"

Go Back!

December 2016

It was a beautiful night, Marinette thought as the wind rushed past her.

For a second she thought she saw copies of herself falling with her and then she knew no more.

Go Back!

October 2016

"Gabriel? Why hasn't Adrien visited yet?" Emilie murmured anxiously as he enters alone, "Does he not wish to see me?"

A dark shadow crossed his face, as he fell to his knees, "Emilie, my dearest I should have told you earlier, but I had hoped," his voice trailed off.

"Told me what?" A feeling of dread washed over her "Gabriel, where is my son?"

"Emilie," tears fell from his face "Adrien he-" his voice broke into sobs,

"No," she cried "No, he can't be."

Gabriel grasped her hands "He m-made an a-attempt," he sobbed head down.

A wounded cry escaped her, as she pulled her hands away as she curled into a ball crying out for her son, who lay just next door. For a moment, his eyes and hands appeared to twitch.

Go Back!

September 2016

Adrien felt himself land on the ground, "I failed?" he whispered, touching his bare finger. With a grunt, he pulled himself up.

As he made his way out of the alley, there was no doubt in his mind Marinette was Ladybug and akumatised.

He'd failed them both just now, but he won't fail again.

Go Back!

September 2016

Marinette Dupain-Cheng was his finest Akuma, she had already managed to get the Ladybug earrings and was now facing off with Chat Noir.

Her fingers grasped his ring Gabriel thought he heard a sorry as Chat Noir cried out "Cata-

She kicked his stomach sending him flying she turned away.

"I've secured both Miraculous Hawkmoth," she said flatly.

"Good job Princess Justice, now bring them to me."

3rd September 2014

"Many centuries ago, magic jewels with extraordinary powers were created," Nooroo began (again).

In Order to Move On, You Must First be willing to Let Go.

Author's Notes:

So I don't really write Dark fic's so this was a bit of a challenge there are a few things I still want to fix in this fic but I'm pretty happy with how it turned out.

Yes, they are stuck in a time loop. In Chloe's part, her writing on the wall survives every loop, in Nino and Alya's second part the Italic writing is them half remembering other loops, and Marinette sees the other loops right before she hits the ground.

If you have any other questions feel free to ask in the comments.