Looking on the internet deeply has found these results:

I would have regretted it if I would agree to marry you is the most popular phrase on the web.

I would have regretted it if I did agree to marry you 11 results on the web	I would have regretted it if I would agree to marry you 12 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
I would have regretted it if I hadn't. But I would have regretted it in the morning. And that's the story of how dying my hair blond kept us from doing something we both would have regretted that night. I would have regretted not seeing you again, especially now that you're you, and the proper size. I might have let you fix the books, and I know I would have regretted it. I would've regretted it if I had left without seeing your blood. Something I would have regretted my entire life. And that's the story of how dying my hair blond kept us from doing something we both would have regretted that night.	But I would have regretted it in the morning. Something I would have regretted my entire life. And that's the story of how dying my hair blond kept us from doing something we both would have regretted that night. I might have let you fix the books, and I know I would have regretted it. He then asked me if I would agree to play his 5th concerto. I would have regretted not seeing you again, especially now that you're you, and the proper size. I would have regretted it if I hadn't. I would've regretted it if I had left without seeing your blood.

I would have regretted it if I did agree to marry you

11 results on the web

I would have regretted it if I would agree to marry you

12 results on the web

More popular!

I would have regretted it if I hadn't.
But I would have regretted it in the morning.
And that's the story of how dying my hair blond kept us from doing something we both would have regretted that night.
I would have regretted not seeing you again, especially now that you're you, and the proper size.
I might have let you fix the books, and I know I would have regretted it.
I would've regretted it if I had left without seeing your blood.
Something I would have regretted my entire life.
And that's the story of how dying my hair blond kept us from doing something we both would have regretted that night.

But I would have regretted it in the morning.
Something I would have regretted my entire life.
And that's the story of how dying my hair blond kept us from doing something we both would have regretted that night.
I might have let you fix the books, and I know I would have regretted it.
He then asked me if I would agree to play his 5th concerto.
I would have regretted not seeing you again, especially now that you're you, and the proper size.
I would have regretted it if I hadn't.
I would've regretted it if I had left without seeing your blood.