He regretted making that decision at once.
I regret spending so much money on that car.
I regret that you didn't pass the test.
I regret calling him.
He told me he regretted that he cannot come.
He regretted for his decision at once.
I was very regretful that spending so much on this car.
I regretfully told you that you haven't passed the exam.
I regretted that I called him.
He told me regretfully that he can't join the party.
4, I regretted having ring him up
5, He regretted to tell me that he couldn't come to the party
I felt very regreted spending too much on cars.
I regret very much to tell you that you don't pass the exam.