"He is strong."
Translation:Il est fort.
Sometimes "l'homme fort" can be figuratively used to refer to a powerful man at the head of a state. Secondarily, "un homme fort" is also used as a polite description of a fat man (same for "une femme forte").
Un homme puissant is a powerful man, in all senses of the word (muscular, influential...)
By the way, seen from France, "Parisian French" sounds very weird to refer to "le français de France".