blackguardly vs scoundrelly

blackguardly and scoundrelly both are adjectives.

Word	Noun	Adjective	Verb	Adverb
blackguardly	No	Yes	No	No
scoundrelly	No	Yes	No	No

As adjectives, blackguardly and scoundrelly are synonyms defined as:

Other synonyms of blackguardly include rascally, roguish.

blackguardly (adjective)	scoundrelly (adjective)
lacking principles or scruples	lacking principles or scruples