Chara Dreemurr

Chara is the first Fallen Child that entered Mt.Ebott. Chara was found by Asriel Dreemurr and they became best friends. But as time went on with her new family with Asriel, Asgore, and Toriel, Chara grew bored over time and gave into genocide, killing every monster she ran into until she gained enough power to destroy the world, over and over again. The betrayed Asriel defeated Chara, but Charas Determination fused Asriel to a flower. Chara must possess Frisk in every timeline in order to kill everything again and again, all for the pleaure of causing despair and pain.