"Know how sublime a thing is to suffer and be strong"

[Above quote by Longfellow]

The conceptualization of strength is domain-dependent. One can have great "strength" as a researcher, and that is a very different type of "strength" than that of a professional wrestler (and someone can be strong in some cases and not in others). It is also culturally-dependent. The way I would answer the question depends on which of my cultures, or sub-cultures I am answering for.
Mass-American Culture: Power (can be good or bad)
Psychology: Resilience (good)
Indonesian Culture as I experienced it: Bisa latihan, bisa bicara, BISA! (Basically "ableness"; good)
As a woman: The ability to "do it all" despite hardships (career, marriage, children; good)

Each of these answers are framed through the various lenses of my cultures and the intersectionality between my cultures. So basically, the question is too simple.

Strength in Nietzsche is represented as the archetypal Greek statesman-warrior. Odysseus would probably be a good example. There was also an interesting note on killing as an expression of strength, and how you cannot separate the expression from the actor of the expression (in this case a bird of prey).

~Tara

"Greatness lies not in being strong, but in the right use of strength." --Henry Ward Beecher