Diabolical
'diabolical' is the definition.
(I know that diabolical can be written as fiendish)
This is all the clue.
(Other definitions for fiendish that I've seen before include "Finished (anag) - demonic" , "This Sudoku" , "like some Sudokus" , "Extremely cruel" , "Diabolic" .)
'diabolical' is the definition.
(I know that diabolical can be written as demonic)
This is the entire clue.
(Other definitions for demonic that I've seen before include "Inspired as if by a fiend" , "As if possessed by devil" , "Like a devil or evil spirit" , "Wicked" , "Devilish" .)
'diabolical' is the definition.
(similar in meaning)
This is all the clue.
(Other definitions for evil that I've seen before include "Maleficent" , "heinous" , "Live (anag.)" , "Nefarious" , "source of harm" .)