The way the characters obliterate the opponent is unique to each of them. If you win, you can decide to deliver a final blow and turn them into dust, or leave them be to spare them.
(Music Mettaton is not being played as) By Design by WRLD (Music if Mettaton is being played): Metal Crusher Remix by Rapwned. (Music): Asgore Orchestral Suite by Laura Platt (Music): Here We Are Remix by Tancla Stuff