devilishly vs diabolically

devilishly and diabolically both are adverbs.

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

As adverbs, devilishly and diabolically are synonyms defined as:

Other synonyms of devilishly include fiendishly.

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