She looked back on the past without regret.
她回首往事毫无遗憾。
It is to be regretted that so many young people leave school without qualifications.
遗憾的是那么多年轻人不能毕业。
It is with great regret that I accept your resignation.
接受你的辞呈,我感到非常遗憾。
A person who does a regrettable action is often regretful afterwards.
行为不检点的人,日后往往懊悔。
One can imagine how regretful he was.
可以想像他是多么懊悔。