heaviest

of comparatively great physical weight or density;
unusually great in degree or quantity or number;
of the military or industry; using (or being) the heaviest and most powerful armaments or weapons or equipment;
marked by great psychological weight; weighted down especially with sadness or troubles or weariness;
usually describes a large person who is fat but has a large frame to carry it
(used of soil) compact and fine-grained;
darkened by clouds;
of great intensity or power or force;
(physics, chemistry) being or containing an isotope with greater than average atomic mass or weight;
(of an actor or role) being or playing the villain;
permitting little if any light to pass through because of denseness of matter;
of relatively large extent and density;
made of fabric having considerable thickness;
prodigious;
full and loud and deep;
given to excessive indulgence of bodily appetites especially for intoxicating liquors;
of great gravity or crucial import; requiring serious thought;
slow and laborious because of weight;
large and powerful; especially designed for heavy loads or rough work;
dense or inadequately leavened and hence likely to cause distress in the alimentary canal;
sharply inclined;
full of; bearing great weight;
requiring or showing effort;
characterized by effort to the point of exhaustion; especially physical effort;
lacking lightness or liveliness;
(of sleep) deep and complete;
in an advanced stage of pregnancy;

heaviest is a valid Scrabble (US) TWL word

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

heaviest is a valid Scrabble Word in International Collins CSW Dictionary

heaviest is a valid Words With Friends word