What is another word for Fiendish?
Pronunciation: [fˈiːndɪʃ] (IPA) 
Fiendish is a word that denotes wickedness or cruelty, which makes it apt to search for synonyms that capture the same sentiment. Some of the synonyms for fiendish are devilish, demonic, hellish, sinister, diabolic, malevolent, malicious, and evil-minded. Other words that can replace fiendish in some contexts include malignant, nefarious, sadistic, vicious, and monstrous. These synonyms all convey a sense of malevolence, wickedness, or evil scheming that can be used both for people and situations. So, if you want to use a term that has the same connotation as fiendish, any of the above words will suffice.
