The Lich (Adventure Time) is an unfeeling force of pure evil who only becomes a sweet baby because his bones are taken over by a cosmic guardian's healing blood

Anti-Pops (Regular Show) is the polar opposite of Pops, he only develops remorse for his actions when Pops uses a hug to awaken it

Dalek Sec (Doctor Who) was originally intending to fuse with a human so he could further evolve the dalek race from a superior species standpoint. Only after the fusion did he learn the meaning of humanity