FTP, name this Byzantine emperor, often given the title "the Bulgar-slayer."
He never married, and was succeeded on the throne by his incompetent brother, Constantine VIII.  Eldest son of Romanus II, the first thirteen years of his actual reign were overshadowed by revolts by Bardas Scleros and Bardas Phocas.  Theoretically emperor from early childhood, his developing years were spent in the shadow of Nicephoras Phocas and John Tzimices.  Defeated in 986 by a force under Samuel at Trajan's Gate, his subsequent military campaigns until his 1025 death were all victorious.  He conquered Armenia to the east, but is more often associated with the peoples to the west whom he massacred.  FTP, name this Byzantine emperor, often given the title "the Bulgar-slayer."
He never married, and was succeeded on the throne by his incompetent brother, Constantine VIII.  
Basil II (accept early Basil the Bulgar Slayer)