"Gladiator"
Reprinted from Superman (Vol 2) #32 -- Superman battles Mongul in his arena.
"Exit to Eden"
Reprinted from Showcase '95 #7-8 -- Mongul escapes captivity and conquers a peaceful planet, eventually exterminating its populace.
"Running Away"
Reprinted from Flash (Vol 2) #102 -- Flash, newly-returned from the Speed Force and supercharged with power, battles Mongul, who has been rampaging through Keystone City.