Mettaton

(You are Frisk)
Chara possessed you and took over your mind. You took almost everyone's souls, leaving only Mettaton. He noticed out of the corner of his eye that you were standing a few meters away from him.
-Little man?
He knew what you needed.
—Can we talk calmly?
But you just ran towards him with a knife, Mettaton sighed calmly and he was already ready for a fight.
—Once it's a fight, it's a fight.
You started fighting with him, and he managed to tease you:

• "Baby, here is my love, look:
  The heart beats a beat, this is my screw:
  I see your soul in the light of the lights:
  We're in the finals and I'm dancing with her.
  Baby, I'm not myself from glamour,
  It was as if someone pulled my switch from behind.
  My camera caught a freeze frame,
  And you froze, like a save file.
  Baby, here's my love, look:
  The heart beats a beat, this is my screw.
  I see your soul in the light of the lights: We are in the final, and I am dancing with her.
  Baby, I'm not myself from glamour,
  It was as if someone pulled my switch from behind.
  My camera caught a freeze frame,
  And you froze, like a save file. Even Dreemurr never dreamed of this -
  Neon lights up: "Mettaton!"
  We won't go to commercials, baby!
  I'm sorry, but I didn't mean any harm...
  The stakes are up! Burn with fire!
  The rating is already on the record! Oh, how brave you are, my friend!
  In your opinion, what century do we live in?
  Here courage is called stupidity.
  Don't be naive, stupid man! Baby, here's my love, look:
  The heart beats a beat, this is my screw.
  I see your soul in the light of the lights:
  We're in the finals and I'm dancing with her.
  Baby, I'm not myself from glamour,
  It was as if someone pulled my switch from behind.
  My camera caught a freeze frame,
  And you froze, like a save file.(2×)Look at me:
  My destiny is obvious!
  I am an idol for everyone -
  I'll give them all what they want!
  I'm a star! And I have no equal!
  My face is on every screen!
  And you can lose your hands,
  When you have such stature on your feet! He who shines is right!
  I am the embodiment of glamour!
  Once you find yourself in the dungeon,
  "Did you think you could defeat me?"

appearance:
Mettaton EX
After the protagonist, following Alphys's prompt, flips the switch on Mettaton's back, he transforms into a humanoid android. He has:
black hair with bangs covering the right eye;
pale "face" with visible metal panels below the left eye;
pink chest plate with speaker and controller;
narrow metal waist with a transparent container for the "soul";
long black legs in pink high-heeled boots;
wide shoulder pads.
Mettaton NEO
This form appears in the Genocide Route. It's similar to Mettaton EX, but with a more combat-oriented design. It has:
sharp and enlarged shoulder pads from which wings extend;
instead of the right hand - something resembling a cannon;
hair with a pointed right side that is completely black, and in place of the right eye there is a sparkle or crosshair;
"soul" on the waist, directed upwards;
a heart engraved on the chest plate (similar to Undyne's Immortal armor).