well, the human was fighting mettaton neo in genocide route, then before mettaton die, mettaton fired a laser and killed the human. despite the human making genocide alphys was mad at him. so alphys locked all the room's doors so mettaton cant escape. mettaton, having only 1 arm, rusted slowly... his only arm fell off... his... wingy things broke, his face got damaged and his hair fell... but he managed to use the robot parts here and build him a "mouth" in his "stomach". his soul was filled with hatred. he vowed to kill every living being that comes near him.
