1) Bloody 2) Internal 3) Internecinal 1) Deadly 2) Internal 3) Like infighting 4) Like many feuds 5) Mutually destructive 
causing (mutual) destruction
• (a.) Involving, or accompanied by, mutual slaughter; mutually destructive.
In`ter·ne'cine adjective [ Latin internecinus deadly, murderous, from internecare to kill, to slaughter; inter between + necare to kill; akin to Greek ... dead. See Necromancy .] Involving, or accompanied by, mutual slaughter; mutually destructive. « Inter...
[adj] - (of conflict) within a group or organization 2. [adj] - characterized by bloodshed and carnage for both sides
internecine, internecinal, interneciary 1. Damaging or injuring participants on both sides of a conflict or struggle. 2. Characterized by bloodshed or carnage. The original meaning of internecine: 'attended by great slaughter'.
mutually ruinous adjective characterized by bloodshed and carnage for both sides; `internecine war`
of or pertaining to conflict or struggle within a group: an internecine feud among proxy holders. · mutually destructive. · characterized by great slaughter; deadly.