Dapper Blook
Napstablook hovered over the remains of his cousin. Mettaton's shattered form was scattered about and her soul was gone. Staring at the remains roused him from his permanent disappointment. Thoughts ran through his mind at the culprit. When he realized who it must have been he howled in rage. The broken bits of Mettaton flew around him and reformed into a new body. Napstablook knelt down over Mettaton's core.
"I will avenge you." He whispered.
In the castle…
Sans was panting as the human evaded the last of his attacks. He could only watch as she advanced with her psychotic smile.
"Your not going to hurt anyone else." Napstablook announced.
The skeleton and human looked at him. He was a metallic human similar to Mettaton but he wore a suit, carried a cane and a black top hat.
"Who the hell are you supposed to be? Harry Houdini?" Chara laughed.
Napstablook ignored her and sprinted to Sans. Chara didn't even realize he was there for a moment.
"How did you?!" She asked starting to panic.
"You killed my family. You've murdered so many innocents in the underground. No more. I've never embraced my power before. Now you'll see what a real ghost can do." Napstablook said holding out his top hat like a cannon.
"What gonna pull a rabbit out of there?" Chara asked.
He didn't answer instead a deafening cacophony of noise burst forth from the hat. Chara's knife flew from her hand and she tried to reach her save file but couldn't through the noise. Napstablook advanced towards her and pinned her to the ground with his cane.
"Your journey ends here." He said as he crushed her soul.
The hall was silent as Sans stared at the metal man in front of him.
"Is that really you?" Sans asked.
"Yes. It seems I am unable to return to my incorporeal form." Napstablook said as he twirled his cane.
"What happened to you? You beat her like it was nothin. She didn't stand a ghost of a chance." Sans said.
"I've always had power. More than Metta or Danny. I never guessed how much it was though. Can the king use this?" Napstablook asked gesturing to the broken soul.
"Nah. Guess we have to wait for another human." Sans said.
"Then I'm headed home." Napstablook said.
"Just like that? Not even gonna stay for tea with Asgore?" Sans asked.
Napstablook stopped at the mention of tea.
"Very well. But call me Dapper Blook." He said.
Dapper Blook then went on to become a successful DJ in the underground and later on the surface.
Sans became a professional gambler with his uncanny ability to predict how things will happen.
Asgore remained underground even after the barrier was destroyed, still mourning the loss of his wife and son. Some say a talking flower kept him company.
Doctor Alphys, debased by the loss of Undyne left the underground after the barrier was destroyed and went to Japan. She was never heard from again.
Muffet opened a bakery on the surface and reunited all of the spiders in the world. Most humans refuse to visit her shop.
Monster Kid never got over Chara's killing spree and was an anti human supporter for the rest of his life.
The other survivors of the massacre scattered around the world and settled in their own places.