isles - He “took many” of the isles in the Aegean in his war with the Romans, and crossed the Hellespont.
prince for his own behalf shall cause the reproach ... to cease - Lucius Scipio Asiaticus, the Roman general, by routing Antiochus at Magnesia (190 b.c.), caused the reproach which he offered Rome by inflicting injuries on Rome’s allies, to cease. He did it for his own glory.
without his own reproach - with untarnished reputation.