Sorry, I'm (really/so/terribly) sorry.
对不起。我感到（实在∕很∕非常）抱歉。

Apologize. Please accept my apology.
我道歉，请接受我的道歉。

I feel really bad about...
我对（某件事）感到非常抱歉。

I didn't mean it.
我不是故意的。

It's all my fault.
全是我的错。

How could I be so thoughtless?
我怎么会那么粗心大意呢？

How can I make it up to you?
我要怎样才能补偿你？

I'll never forgive myself.
我永远不能原谅自己。

Will you ever forgive me?
你会原谅我吗？