I've so many things I would consider a final straw now looking back, but the apparent final straw was being choked!
Really, if I could turn back time I'd have ended it years and years ago, when he insisted on his jobs and my jobs, but his jobs never got done and I was expected to be sympathetic because "depression", but when my jobs didn't get done because I was burnt out I obviously had to step my game up because living in squalor was making his depression worse so if I loved him, I'd remember to do all these things.
In fact, scratch that, I'd go back even further in time, and my last straw should have been working overtime while he takes time off to recuperate, meanwhile he was ordering dominos 5 times a week, getting us more in debt, because he was too "depressed" to cook from the food I'd bought on a budget to tide us over while I worked us out of our overdrafts.
In fact, scratch THAT, my final straw should have been not falling for his nice facade of him not being like his family who are violent, sexist, mysoginistic wastes of space. You are the company you keep, and in his case both nature and nurture were against him.