Translation of "Could've" in Korean

He could've quit,

그는 포기할 수도 있었지만

They could've just asked women about their experience.

여성들에게 그들의 경험을 그냥 물어볼 수도 있었는데 말이죠.

I feel like I could've been a slightly better son to them.

이럴 줄 알았으면 말 좀 잘 들을 걸 그랬네요

But do you think there was a faster way that you could've delivered the medicine?

약품을 전달할 더 빠른 길이 있었다고 생각하시나요?