gladiator vs fighter

gladiator and fighter both are nouns.

Word	Noun	Adjective	Verb	Adverb
gladiator	Yes	No	No	No
fighter	Yes	No	No	No

As nouns, fighter is a hypernym of gladiator; that is, fighter is a word with a broader meaning than gladiator:

gladiator: (ancient Rome) a professional combatant or a captive who entertained the public by engaging in mortal combat
fighter: someone who fights (or is fighting)

Other hypernyms of gladiator include battler, belligerent, combatant, scrapper.

gladiator (noun)	fighter (noun)
(ancient Rome) a professional combatant or a captive who entertained the public by engaging in mortal combat	a high-speed military or naval airplane designed to destroy enemy aircraft in the air
a professional boxer	someone who fights (or is fighting)
	someone who fights for a cause