gladiator vs battler

gladiator and battler both are nouns.

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

As nouns, battler is a hypernym of gladiator; that is, battler 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
battler: someone who fights (or is fighting)

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

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