In shows where mano-a-mano combat is a main plot element, characters spend much of their lives training and improving their strength so they can one-up each other at a critical point in a fight. This invariably develops into an arms race that can, and has, taken out entire planets and solar systems.
This has a grain of truth in it, as between two equally skilled fighters, the deciding factor will often be one’s strength.
Compare Weak, but Skilled, and contrast Unskilled, but Strong. If two nations do this, it’s a Lensman Arms Race. When the situation is about equipment and weapons rather than physical prowess, see Bigger Stick. If two Rules Lawyers do this, it’s My Rule-Fu Is Stronger Than Yours. Also The Greatest Style, where one form of “kung fu” really is stronger than another.