finishing touches; last vital touch
A yojijukugo meaning the final crucial detail that brings a work to life. Often used in the phrase 画竜点睛を欠く (to lack the finishing touch).
His speech was excellent, but it lacked the finishing touch in the final remark.
この絵はあと一筆で画竜点睛となる。
This painting will be complete with just one more stroke as the finishing touch.