Wiktionary
deader than a doornail
a. (context humorous English) (alternative form of dead as a doornail English)
Usage examples of "deader than a doornail".
A handful of the pretty green leaves can kill you deader than a doornail.
Kind of the way a bug looked flipped on its back, legs stiff, deader than a doornail.
He'd actually been deader than a doornail and death had been just as delightful as he'd dreamed it would be.