weakest

wanting in physical strength;
overly diluted; thin and insipid;
(used of vowels or syllables) pronounced with little or no stress;
wanting in moral strength, courage, or will; having the attributes of man as opposed to e.g. divine beings;
tending downward in price;
deficient or lacking in some skill;
lacking bodily or muscular strength or vitality;
(used of verbs) having standard (or regular) inflection
not having authority, political strength, or governing power;
deficient in magnitude; barely perceptible; lacking clarity or brightness or loudness etc;
likely to fail under stress or pressure;
deficient in intelligence or mental power;

weakest is a valid Scrabble (US) TWL word

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

weakest is a valid Scrabble Word in International Collins CSW Dictionary

weakest is a valid Words With Friends word