The Tu-Toriel

Ṋ͎̙͕A̱̹͉̙M̀E҉ ͏͉̤̮̱̰͇T̡͍͔̣͍̯̟H̻̮̱̹̲̖̘͜E̮̭̫̣̤ ͇F̢̻͖̳̥̝̦A̞̦̦̯̙̜̯L͡L͔E̼̗͍̗̜N͕͠ ̨̼͇H̰̜͢U̵͕̫͎͚̩̹M̶̟̥̜A̷̲̘N̢̠̬̬

Y/n. She appears only rarely. Few timelines contain her, instead of Frisk.
And in this one, she has chosen to commit Genocide.