call into question vs oppugn

call into question and oppugn both are verbs.

Word	Noun	Adjective	Verb	Adverb
call into question	No	No	Yes	No
oppugn	No	No	Yes	No

As verbs, call into question and oppugn are synonyms defined as:

call into question and oppugn: challenge the accuracy, probity, or propriety of

Other synonyms of call into question include question.

call into question (verb)	oppugn (verb)
challenge the accuracy, probity, or propriety of	challenge the accuracy, probity, or propriety of