lower-ranking vs lowly

lower-ranking and lowly both are adjectives.

Word	Noun	Adjective	Verb	Adverb
lower-ranking	No	Yes	No	No
lowly	No	Yes	No	No

As adjectives, lower-ranking and lowly are synonyms defined as:

Other synonyms of lower-ranking include junior-grade, petty, secondary, subaltern.

lower-ranking (adjective)	lowly (adjective)
inferior in rank or status	low or inferior in station or quality
	inferior in rank or status
	of low birth or station (`base' is archaic in this sense)
	used of unskilled work (especially domestic work)