Italian word combattente comes from Latin con-, Latin batto, and later Latin *combatto ((Vulgar Latin) I combat.)

Detailed word origin of combattente

Dictionary entry	Language	Definition
con-	Latin (lat)	Used in compounds to indicate a being or bringing together of several objects. Used in compounds to indicate the completeness, perfecting of any act, and thus gives intensity to the signification of the simple word.
batto	Latin (lat)
*combatto	Latin (lat)	(Vulgar Latin) I combat.
combattere	Italian (ita)	(intransitive) (figuratively) to fight, to battle, to shrive. (intransitive) to fight, to combat. (transitive) to fight, to combat, to oppose.
combattente	Italian (ita)	Fighter, combatant Fighting, combatant.

Words with the same origin as combattente