Greatest is an adjective. It has no plural because it is not a noun.
antidisestablishmentarianism
tattarrattat
SD max
If your question is correct, there is no such thing as that; if it isn't, then it's either the least common factor, or the greatest common denominator.
Wit beyond measure is man's greatest treasure.
The word greatest has two syllables. Great-est.
Best, or largest.
Greatest is an adjective. It has no plural because it is not a noun.
laid
That was the greatest thing I've ever seen. His was the greatest act of sacrifice anyone had heard of.
God (Allah)
Best and Greatest
antidisestablishmentarianism
tattarrattat
The GCF or greatest common factor.
If your the greatest of all time you would be called either an "over lord" or "the greatest of all time".
dominant