Sora approached the elevator, and got inside of it. He clicked the button, and found himself rising forward to the top of the core. At the top, he saw a large doorway. He entered it, and saw a painfully familiar face waiting on the other side.
"Well, well, well." Mettaton announced. "I see you've finally arrived, to this, the grande finale of our show!"
"What are you talking about?"
"Oh, don't play dumb darling!" Mettaton shouted at him. "We've all seen you! Determined on your sudden murderous rampage! First it was Undyne, our true hero, struck down! Then, you decided to attack ME! And on live television!" Sora started to feel regret for the actions that had been carried out. "Now, we can all see what's going to happen, now that we stand face to face! I must stand in your way!" Mettaton popped his robotic knuckles. It produced the sound of gunfire.
"You see, as any true fan would know, I was original designed as a human eradication robot!" Mettaton explained, "Unfortunately for you, those features have never been fully removed! Take another step forward, and I'll be forced to show MY TRUE FORM!"
Smoke covered the floor of the platform the found themselves on. Spotlights spun around. Fire blared from either side of the stage. Sora summoned his keyblade, and prepared for a fight to the death.
"FINE THEN!" Mettaton said, reaching for the switch on his back. "IT'S SHOWTIME DARLING!" He flipped the switch and Sora saw him transform into a humanoid shape with wings on the back. It had a gun for one of its hands. "ALLOW ME TO INTRODUCE..." A song started blasting through the air. He shot several bullets from his hand into the air as the spotlights shifted onto him. "METTATON NEO!"
Sora started running towards Mettaton. He took a swipe with the keyblade, but missed. Mettaton knocked him to the ground, but he dodge rolled and stood up. He ran towards Mettaton, weapon drawn, and attacked him, hitting him directly in the chest. Mettaton fell to the ground. The music stopped.
"I... suppose she... should've worked more... on the defenses..." Mettaton said, grasping for life. "But... You..." His face looked pained. "Once you reach the surface... You won't harm humanity... Will you? Are you... Entirely evil?"
He collapsed into a useless pile of metal. Sora stood up and started walking forward.
...
Alphys entered the room. She had seen he creation... No, her friends final performance, live. She had sat and viewed from a tablet as her last true follower spoke his final words. And did nothing.
"Mettaton..." She whispered, "No..."
Her glasses were fogged with tears. Despite this, she still saw the figure of Sora, walking into the next room.
She stated under her breath, through gritted teeth,
"...You killed everyone I loved..."