I'm sorry. （假客气的时候说，并不真的觉得抱歉。）
I'm sorry, but you don't know what you're talking about.
不好意思，你说什么？（你知道你自己在说什么吗？）

sorry? （=pardon？）我没听懂，我没听清！
Sorry? what was that again?
不好意思，你刚才说什么？

Sorry？（质问的语气）你说真的吗？你说什么？

You'll be sorry. 你会后悔的。
If you don't finish your homework before mom gets home, you'll be sorry.
如果妈妈回家前你还没写完作业，你会后悔的。
You'll be sorry when your girlfriend finds out you went drinking last night.
要是你女朋友发现你昨晚出去喝酒了，你就会后悔的。
If you don't get that done, you'll be sorry.
要是你没完成这件事，你会后悔的。

better safe than sorry 小心为上，不要事后后悔莫及
Put your seat belt on-better safe than sorry.
系好安全带，不要事后追悔莫及。
Set the alarm clock-better safe than sorry.
订好闹钟，不要到时候后悔。
Watch your purse-better safe than sorry.
看好你的包，不要到时候后悔。