completing vs complemental

completing and complemental both are adjectives.

Word	Noun	Adjective	Verb	Adverb
completing	No	Yes	No	No
complemental	No	Yes	No	No

As adjectives, completing and complemental are synonyms defined as:

completing and complemental: acting as or providing a complement (something that completes the whole)

Other synonyms of completing include complementary.

completing (adjective)	complemental (adjective)
acting as or providing a complement (something that completes the whole)	acting as or providing a complement (something that completes the whole)