What's the adjective for diabolical? Here's the word you're looking for.
Included below are past participle and present participle forms for the
verbs diabolize, diabolify and diabolise which may be used as adjectives within certain contexts.
“Though the words came from the fanged mouth of a diabolical beast from the foulest pit of the Abyss, the tone sounded familiar.”
“The springs themselves were as diabolical in appearance as the witches' caldron in Macbeth, and needed but the presence of Hecate and her weird band to realize that horrible creation of poetic fancy.”
“They were such sly dogs, and disguised their views so well, that there was no getting at positive evidence of their traitorous and diabolical intentions.”