What's the adjective for demoniacal? Here's the word you're looking for.
Included below are past participle and present participle forms for the
verbs demonize, demonise and demonify which may be used as adjectives within certain contexts.
“Barely average height, his flashing, sometimes demoniac approach, which so contrasted with the measured Kemble school, made him one of the most controversial of the early 19th-century actors, generating as much abuse as admiration.”