megalomaniacal

adjective

meg·​a·​lo·​ma·​ni·​a·​cal -mə-ˈnī-ə-kəl 

variants or megalomaniac also megalomanic

-ˈman-ik 

: belonging to, exhibiting, or affected with megalomania

ruled by a megalomaniacal tyrant

megalomaniacally

-ə-k(ə-)lē 

adverb