hardest

not easy; requiring great physical or mental effort to accomplish or comprehend or endure;
dispassionate; ;
resisting weight or pressure
very strong or vigorous;
characterized by effort to the point of exhaustion; especially physical effort;
produced without vibration of the vocal cords;
(of light) transmitted directly from a pointed light source
(of speech sounds); produced with the back of the tongue raised toward or touching the velum;
given to excessive indulgence of bodily appetites especially for intoxicating liquors;
being distilled rather than fermented; having a high alcoholic content;
unfortunate or hard to bear;
dried out;
with effort or force or vigor;
with firmness;
earnestly or intently;
causing great damage or hardship;
slowly and with difficulty;
indulging excessively;
into a solid condition;
very near or close in space or time;
with pain or distress or bitterness;
to the full extent possible; all the way;

hardest is a valid Scrabble (US) TWL word

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

hardest is a valid Scrabble Word in International Collins CSW Dictionary

hardest is a valid Words With Friends word