Asriel Dreemurr

In Undertale, Asriel Dreemurr is the deceased son of Toriel and Asgore and the former prince of the Underground. His adoptive human sibling, Chara, drew him into a plan to collect six human souls from the surface. After Chara died, Asriel absorbed their soul, crossed the barrier and carried their body to the surface, but he refused to fight back against humans who mistook him for Chara's murderer, and they killed him. Alphys later brought him back as Flowey, who lacks empathy and compassion because he has no soul.