(a.) Involving, or accompanied by, mutual slaughter; mutually destructive; as, an internecine battle\.

baneful brutal calamitous cataclysmal cataclysmic catastrophic consuming consumptive deadly death-bringing deathful deathly demolishing demolitionary depredatory desolating destroying destructive devastating disastrous doomful fatal fateful feral fratricidal killing lethal malign malignant mortal nihilist nihilistic pernicious ravaging ruining ruinous savage self-destructive subversionary subversive suicidal vandalic vandalish vandalistic virulent wasteful wasting withering