@Dauntless That's very true. Undertale is quite consciously a storybook universe, a world that literally lives by the rules of adventure games, so of course the underground kingdom would have its fearless warrior. I'll go in for fighting shoggoths or whatever :p
I've been tempted to hypothesize though that the monsters could get rough on each other sometimes. maybe nothing too serious, but heck, we've seen drunk and unhappy monsters, maybe fights break out sometimes.