a.
1.
Hurtful, harmful, deleterious, injurious, detrimental, baneful, baleful, prejudicial, noxious, noisome, mischievous, damaging, disadvantageous, destructive, ruinous, fatal, deadly, malign.
2.
Malicious, wicked, evil-hearted, malignant, malign, mischievous, mischief-making, malevolent.