hellish in WordNet English dictionary

1. very unpleasant
   "hellish weather"; "stop that god-awful racket"
   beastly  hellish  god-awful 
   
2. extremely evil or cruel; expressive of cruelty or befitting hell
   "something demonic in him--something that could be cruel"; "fires lit up a diabolic scene"; "diabolical sorcerers under the influence of devils"; "a fiendish despot"; "hellish torture"; "infernal instruments of war"; "satanic cruelty"; "unholy grimaces"
   demonic  diabolic  diabolical  fiendish  hellish  infernal  satanic  unholy