完勝, 惜敗, and 完敗: how a win or loss unfolded
Compare a 3–0 win and maintained control with a one-point loss and a defeat caused by being unable to match speed, without making a universal score rule.
完勝 (かんしょう): a decisive win
「守備が安定し、決勝では三対零で完勝した。」 (“With a solid defense, we won the final decisively, three to zero.”) The 3–0 result belongs to this match. Do not make conceding zero points a necessary condition for every use of 完勝.
「相手に一度も主導権を渡さない完勝だった。」 (“It was a complete victory in which we never surrendered control.”) The focus is never giving up control. Without a stated score, do not transfer 3–0 or zero conceded points into this example.
惜敗 (せきはい): a narrow, regretted loss
「決勝では一点差で惜敗した。」 (“We narrowly lost the final by one point.”) A one-point loss is reported here. Keep both the small margin and the fact that the side lost.
「惜敗にもかかわらず、観客は選手に温かい拍手を送った。」 (“Despite the close loss, the audience applauded the player warmly.”) The player receives warm applause after the narrow loss. Applause does not turn it into a victory or report a win in a later match.
完敗 (かんぱい): being thoroughly beaten
「決勝では相手の速さについていけず完敗した。」 (“We suffered a complete defeat in the final because we could not keep up with our opponent's speed.”) The loss is described through an inability to match the opponent's speed. That particular cause does not become the cause of every heavy defeat.
「今回の完敗を次の練習に生かしたい。」 (“I want to use this crushing loss to improve our future training.”) The speaker wants to use the defeat in future practice. The wish does not report completed training or victory in a subsequent match.
Does 完勝 always require the opponent to score zero?
Show the answer and why
Do not make that a universal condition. The 3–0 score belongs to one example, while another describes maintaining control. Read each term with the stated manner of winning or losing.