Can it be completely one spouse's fault that the marriage has gone bad?
Probably not. But I think I understand where you are coming from.Do you think its your fault or theirs?
I think it depends on what you are referring to. Addictions (to many things) can easily be a one sided deal breaker. Cheating comes to mind too. What about someone who refuses to work or contribute to the well being of a family in any way. Or someone who is abusive etc. I would think that there are certainly many situations where one is doing their best to work at the marriage/relationship, and the other spouse is doing their best to destroy the marriage through continued bad behavior.
Yes it can, as mentioned above. BUT often one person blames another and it isn't. So there is no simple answer to this question.
"It's all your fault" means:
"I take no responsibility for anything."
You cannot carry two people on your one set of shoulders.
Yes it is possible that it can be one spouse's fault that the marriage has gone bad. You need to be more specific in giving us the situation to get more input. There are all types of addictions and if a spouse decides that something or someone is more important than the person they are married too yes they can ruin the marriage.