The Sin of Death-Seven Deadly Sins, The Eighth Sin

Kara is the Eight sin. The sin of death. She got her sin when going berserk as a child after an argument with her adopted family. She murdered them and the rest of the town, leaving it in pieces. She happens to be Meliodas's sister. Meliodas had a demon father and goddess mother, like Kara. He only got demon genes but Kara got both. After she firsthand witnessing Meliodas being murdered, she helps the other sins fight the demons. But that's way after she meets the other sins...