virulent

extremely poisonous or injurious; producing venom; "venomous snakes"; "a virulent insect bite"

infectious; having the ability to cause disease

harsh or corrosive in tone; "an acerbic tone piercing otherwise flowery prose"; "a barrage of acid comments"; "her acrid remarks make her many enemies"; "bitter words"; "blistering criticism"; "caustic jokes about political assassination, talk-show hosts and medical ethics"; "a sulfurous denunciation"; "a vitriolic critique"