What if Riposte didn't let herself be turned away from the challenge to Adrien? Warning: violence.
Riposte Lets Rip
Chapter 1: Challenge
Kagami tried to reach her mother when her driver stopped at a red light.
"I'm not available at the moment. Leave a message," said the voicemail prompt.
"Mother, you thought I was good enough, but... I lost," said Kagami. "I won't be joining the D'Argencourt Academy,"
Kagami looked down the insignia on her ring, the "Ken no Onna," or "Sword Woman." How could she have lost? She came from generations of fencing champions!
Her mother would never forgive her for losing. There were no second chances in her family. It wouldn't matter that he had cheated, using a biased referee. She should have won so decisively that nobody could have claimed otherwise.
An akuma squeezed in through the car window. It entered the ring on Kagami's right hand. She sat up glaring, all her vengeful emotions amplified.
"Riposte! I am Hawk Moth," said a voice in her mind. "I'm giving you a second chance to prove that you are the best fencer of all, but in return, you must bring me Ladybug and Chat Noir's Miraculous."
"On my honor, Hawk Moth, I shall be victorious!"
Purple magic fluttered all around her – she gained metallic armor and a sword attached to her right arm. As the light turned green, Riposte sliced open the sun roof and leaped out of the car.
Her opponent was in the car following hers. Riposte slashed at the car, cutting it in two. The front half crashed, knocking out the muscular driver. Adrien was thrown out, but he rolled, not taking much damage.
"I'm taking you up on your offer of a decisive match!" said Riposte.
"I- I can't fight you like this! You're not... yourself," said Adrien.
"Halt, Riposte!" said Hawk Moth in her mind. "You may seek your revenge, but only after you take hold of Ladybug and Cat Noir's Miraculous first."
Riposte let her intense desire for revenge overwhelm her new loyalty to Hawk Moth.
"I hear you, Hawk Moth. But..."
Adrien started to run.
"It is dishonorable to run from a challenge!" said Riposte.
Fast as thought, she slashed with her blade. Adrien was cut through the heart. He died instantly.
"What have you done! You've killed him, you've killed my son!" sent Hawk Moth.
"With the power you gave me," said Riposte.
Hawk Moth sent a burst of pain, sending her to her knees. The akuma flew out from her and the power was gone. Unlike when an akumatized object was broken, Kagami returned to normal with all the memories of what she had done.
Kagami was frozen with shock and horror.
Ladybug arrived and ran to the fallen boy. "No! Adrien! I was too late!"
Ladybug raised her head and howled with grief. Then she saw the akuma butterfly flying away and instinctively went through the ritual to capture and purify it.
"Bye-bye, little butterfly," said Ladybug, but her tone was bitter.
"The only hope for Adrien is the healing spell," said Ladybug to herself. "Lucky..."
She tried to send her yo-yo into the air, but something black grabbed it.
"No, not now," said the little creature.
"What are you?" asked Ladybug. "You look like a dark version of Tikki. Why are you trying to stop me?"
"I'm Plagg, the Cat kwami. You can't do a Lucky Charm now. Not if you want Adrien alive again."
"Why?" asked Ladybug.
"Since your Lucky Charm didn't help stop the akuma, the Miraculous Ladybug spell will be weak. Bloodshed by an akumatized weapon is the toughest damage to fix."
"Wait, if you're the Cat kwami, you must work with Chat Noir. Where is he? Why aren't you with him?"
"I'm severed from him – because he died."
"B-but, that means... Adrien is Chat Noir?"
"He was. Yes."
"I have to get him back. What do I have to do to get a healing charm powerful enough?"
"You need to face the master of all the akumas, Hawk Moth. Defeat him using a Lucky Charm and you'll have the power to heal Adrien."
"Me against Hawk Moth? Alone?" asked Ladybug. "I have to try... of course. Nothing matters but saving Adrien."
"Let me help you," said Kagami, standing up. "Hawk Moth used me. He got me to attack with super powers against a helpless opponent. He has soiled my honor and he must pay."
"I'm sorry, but I can't involve a civilian," said Ladybug.
"I could power her up as a new Chat Noir," said Plagg. "You're going to need all the help you can get."
"Yes, let me do that!" said Kagami.
"No. I can't let anyone else get killed," said Ladybug.
"I can fight, and this is a matter of honor."
"No."
"I can tell you who Hawk Moth is. Let me be your Chat Noir."
"You know who he is?" asked Ladybug.
"Yes, but I'll only tell you if you let me help," said Kagami.
"All right... I have no choice," said Ladybug.
Plagg got the ring from Adrien's hand and gave it to Kagami. After brief instructions she was ready.
"Plagg, claws out!"
The new suit was sleek, with a ninja-like style. There was no bell.
"Now, what do you know about Hawk Moth?" asked Ladybug.
"He said I killed his son. Hawk Moth is the father of Adrien," said Chat Noir.
"Gabriel Agreste? I suspected him, but I was sure we eliminated him as a possibility," said Ladybug.
"I am sure," said Chat. "Whatever convinced you otherwise, it was a trick."
"Then let's go get him," said Ladybug. "For Adrien."
"For honor," said Chat.
The two headed off to the Agreste mansion. The new Chat Noir was used to weapons and adapted quickly to using the staff.