deadest

no longer having or seeming to have or expecting to have life;
not showing characteristics of life especially the capacity to sustain life; no longer exerting force or having energy or heat;
very tired;
unerringly accurate;
physically inactive;
(followed by `to') not showing human feeling or sensitivity; unresponsive;
devoid of physical sensation; numb;
lacking acoustic resonance;
not yielding a return;
not circulating or flowing;
not surviving in active use;
lacking resilience or bounce;
out of use or operation because of a fault or breakdown;
no longer having force or relevance;
complete;
drained of electric charge; discharged;
devoid of activity;

deadest is a valid Scrabble (US) TWL word

deadest is a valid Scrabble Word in Merriam-Webster MW Dictionary

deadest is a valid Scrabble Word in International Collins CSW Dictionary

deadest is a valid Words With Friends word