Adjectives

(s)barbarous, brutal, cruel, fell, roughshod, savage, vicious(of persons or their actions) able or disposed to inflict pain or suffering“a barbarous crime”, “brutal beatings”, “cruel tortures”, “Stalin's roughshod treatment of the kulaks”, “a savage slap”, “vicious kicks”
(s)evil, vicioushaving the nature of vice
(s)condemnable, criminal, deplorable, reprehensible, viciousbringing or deserving severe rebuke or censure“a criminal waste of talent”, “a deplorable act of violence”, “adultery is as reprehensible for a husband as for a wife”
(s)poisonous, venomous, viciousmarked by deep ill will; deliberately harmful“poisonous hate”, “venomous criticism”, “vicious gossip”