complemental vs completing

complemental and completing both are adjectives.

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

As adjectives, complemental and completing are synonyms defined as:

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

Other synonyms of complemental include complementary.

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