Mettaton

Mettaton is a ghost who lives inside of a robotic body that was built by Dr. Alphys. He was killed by Thanos in Infinity War.

Appearance
Mettaton usually appears to be a metal box with a heavily pixelated screen on it, as well as several knobs, two long arms, and gloved hands. There is a wheel on the bottom of the box. However, in Avengers: Endgame he is only seen in his EX form, where he appears to be a metal human with black hair covering his right eye, eyeliner on his left eye. He wears a purple chestpiece as well as black spikes on his shoulders, with a heart (presumeably his soul) in the middle. He has long legs with purple high-heel shoes.

Story
Mettaton, who disintegrates in Infinity War (leaving his robot body as an empty husk), first appears during Act II as a prisoner in the past where he isn't dead on Thanos's Sanctuary Ship. He helps the Avengers attempt to escape the nomu gauntlet and fight various enemies, but is killed with a bomb by Fassad, who kills Alphys at the same time. Mettaton is next seen when the heroes killed by Thanos are brought back during Act III. In the Final Battle he mainly fights in the background. He attends Deku's funeral.