(a.) Having the quality of injuring or killing; destructive; very mischievous; baleful; malicious\; wicked.

baleful baneful brutal corroding corrosive corrupting corruptive counterproductive damaging deadly death-bringing deathful deathly deleterious destructive detrimental devastating disadvantageous disserviceable distressing fatal feral harmful hurtful injurious internecine killing lethal malefic maleficent malevolent malign malignant miasmatic miasmic mischievous mortal noisome noxious ominous pestiferous pestilent pestilential poisonous prejudicial ruinous savage scatheful sinister swart toxic venenate veneniferous venenous venomous vicious virulent