Synonyms for Hellish (same or very similar meaning)
WordNet sense 1 (very unpleasant):
beastly, god-awfulWordNet sense 2 (disagreeable to the senses, to the mind, or feelings ):
unpleasantWordNet sense 3 (extremely evil or cruel; expressive of cruelty or befitting hell):
demonic, diabolic, diabolical, fiendish, infernal, satanic, unholyWordNet sense 4 (morally bad or wrong):
evilFrom the ODE community, based on WordNetadd/edit