Thanks to Milpup good title! Anyways, it's the SOULs of Frisk and Chara(Genocide specific)... I just felt like putting them together. I couldn't come up with a name, but Mil sure helped me out of that tight spot!
Flowey feels no remorse, Asriel is sorry for his mistake, and in this world, it's Kill or be Killed. Oh, btw, if you haven't played/watched all the way through, this would be considered SPOILERS.