complementing / complimenting are similar-sounding terms with different meanings (referred to as homophones). To better understand the differences, see below for definitions, pronunciation guides, and example sentences using each term. 👇
complementing: (verb) make complete or perfect; supply what is wanting or form the complement to.
complimenting: (verb) say something to someone that expresses praise. (verb) express respect or esteem for.
complementing: k·AA·m·p·l·ah·m·EH·n·t·ih·ng
complimenting: k·AA·m·p·l·ah·m·EH·n·t·ih·ng
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)