Strength is the power to resist force. It can be used in the context as being physical, such as the force in a person or animals muscles. And could also be used as meaning superhuman strength which is a creature being stronger than normally possible. They are frequently used in comic books and video games.
Strength also means "the power to induce the taking of a course of action or the embracing of a point of view by means of argument or entreaty" (e.g. 'The strength of his argument settled the matter')