I tried, but ended up with this:
それは避けられたかもしれない。
But, I do not know if it is right to say it that way
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Sign up to join this communityIt could have been avoided.
それは避けられたかもしれない。
You are right.
Though sentence 5 and 7 are commonly used, I think, sentence 4 and 6 are more natural than sentence 5 and 7 respectively.