Undertale spoilers
@kara_dreamer@witches.town It's implied Chara was... unfortunately, a very bitter and twisted individual, due to their treatment at the hands of their own kind, and instead of finding joy and love and mending their broken heart by finding a family who supported and loved them in Toriel, Asgore and Asriel, it only increased their bitterness. "How dare humans treat their new family like this", sort of thing, leading to their revenge plan, sadly. Asriel tragically was led astray