Okay.
I think I get your intent, now.
"Might" has less probability than "could".
It's hard to tell if I prevented any good "could have been".
Maybe my divorce counts. It "could have been" a good marriage. Then again, it "could have been" a worse situation than ending as friends.
Maybe choosing not to go into computer programming in the 1980s count. I "could have" earned more money. On the other hand, I "could have" been one of those who sold "too early" to Microsoft and be kicking myself now. LOL