Fell Undyne can be extremely mean and brutal when she has to. She usually doesn't really likes killing humans, but she does it because of pressure. The underground seems to be horrified of this guardswoman, as she works directly for the king of the underground. Undyne is very tough and strong, but she could be so gentle to a friend. She's also kind of a disaster, being a bit silly some times, but she's still scary when she needs to be. She is a bit afraid of Alphys but dearly loves her as well.