Answer: internecine

AnswerCrossword Clue
INTERNECINEMutually destructive
INTERNECINEMutually destructive.
INTERNECINELike many feuds
internecinedeadly, murderous also INTERNECIVE
internecineDestructive to both sides in a conflict
internecinemutually destructive.
internecineOf or relating to conflict within a group or organization