Stone dead
Definition 1 of 2
Pro Tip 1/3Irreversible State
Used to stress that death is permanent and there is no coming back. 
After the venom struck, the victim was stone dead.
Pro Tip 2/3Dramatic Effect
Often used in storytelling to emphasize the abruptness or finality of death. 
The hero confirmed the villain was stone dead.
Pro Tip 3/3Not Literal
Can be used metaphorically to describe something completely inert or unresponsive. 
My computer crashed and was stone dead.