diabolically vs devilishly

diabolically and devilishly both are adverbs.

Word	Noun	Adjective	Verb	Adverb
diabolically	No	No	No	Yes
devilishly	No	No	No	Yes

As adverbs, diabolically and devilishly are synonyms defined as:

Other synonyms of diabolically include fiendishly.

diabolically (adverb)	devilishly (adverb)
as a devil; in an evil manner	in a playfully devilish manner
	(used as intensives) excessively
	as a devil; in an evil manner