Translation

補完的な / 互いに補い合う / 組み合わせて効果的な

Meaning

Complementary means that two things work well together because each adds what the other lacks. It is used for skills, colors, products, strategies, and therapies. Do not confuse it with complimentary, which means free or praising.

Examples

• 二人の強みは互いに補完的でした。
  Their strengths were complementary.
• その二つのサービスは競合ではなく補完関係にあります。
  The two services are complementary, not competing.