This Chara is the first human to fall down who ate deadly buttercups in order for Asriel to break the barrier with Chara's soul. Asriel died refusing to fight. For a long time they have remained as a spirit of determination, and now, after you massacred every monster in the underground, they stand in front of you gained human form after absorbing all the love you gained. Now they'll give you the ending to your playthrough. Player. Erase the timeline. Not truly good nor evil.