Internecene
in·ter·ne·cine
/ˌin(t)ərˈˌneˌsēn,in(t)ərˈnēsīn/
adjective
destructive to both sides in a conflict.
"the region's history of savage internecine warfare"
Similar: deadly, bloody, violent, fierce, destructive, ruinous, civil, internal, family
relating to conflict within a group or organization.
"the party shrank from the trauma of more internecine strife"