To settle a dispute or issue; to bring something to a clear conclusion or resolution.
両チームは延長戦で決着をつけた。
The two teams settled it in extra time.
この問題には早く決着をつける必要がある。
This issue needs to be settled quickly.
彼らは互いに話し合って、やっと決着をつけた。
They talked it over and finally came to a resolution.