«عَمْرُو الشُّجَاعُ»
ʿAmr is the brave one.
The utterance may use hyperbolic restriction: ʿAmr possesses courage so excellently that the courage of others is treated as negligible by comparison. This does not entail the literal absence of every other courageous person.
Factual restriction would exclude other actual instances. Rhetorical exaggeration can acknowledge them while using a restrictive form to celebrate one person’s exceptional quality.
The difference is determined by the subject matter, external facts and rhetorical aim, not by the definite article alone.