IPA: /ˈɪnˌfaɪtə/
KK: /ˈɪnˌfaɪtər/
A person who engages in conflict or disputes within a group, often in a competitive or aggressive manner.
The infighter was known for stirring up disagreements among the team members.
Infighter → It is formed from "in-" (meaning within) and "fighter" (from Old English "feohtan", meaning to fight). The word describes someone who fights from within, often used in the context of boxing or combat sports.
Think of someone who is 'fighting from within' ('in-') — that's what an infighter does.