10. Killing Their Grandmother - Carnage #12 (2016)
After almost being strangled by his umbilical cord in the womb, Cletus Kasady was revived by the evil lord of symbiotes, Knull. While this information doesn't initially seem important in regards to him killing his grandmother, it means the villain was custom-built by this god to receive the Carnage symbiote, which means he was born into the world with a lust for blood that would prove completely insatiable.
And Cletus would begin to satiate this thirsty for violence with his own family, starting with their pet dog, before moving onto more human targets - namely, his own grandmother.
After hearing one too many insults from the old woman, Cletus decides to take a short walk with his gran down a long flight of stairs, killing her in his first gruesome murder.
This event would become public knowledge after Jubulile got an accidental look into the villain's memories, which uncomfortably launched her right into Kasady's childhood secrets, and made this awful deed significantly more public.