Synonyms to poison-pen

malicious, acrid, antagonistic, antipathetic, baleful, baneful, belligerent, bitchy, bitter, catty, caustic, clashing, colliding, conflicting, cussed, deleterious, despiteful, detrimental, envious, evil, full of hate, green, green-eyed, harmful, hateful, hostile, iniquitous, invidious, jealous, malefic, maleficent, malevolent, malign, malignant, mean, nasty, noxious, ornery, pernicious, petty, poisonous, quarrelsome, rancorous, repugnant, set against, sore, spiteful, venomous, vicious, virulent, vitriolic, wicked