if (the) worst comes to (the) worst

If the least ideal or preferred outcome happens. Even if worst comes to worst and it rains on our wedding day, we'll make the best of it. I know you don't want to think about it, but, if the worst comes to the worst, what would you do in a zombie apocalypse?

Prov. in the worst possible circumstances; if the worst possible thing should happen. We should be able to catch the four-thirty train, but if the worst comes to the worst, we could get a taxi and still get into town on time. Of course, I hope that your wife's health recovers, but if worst comes to worst, I want you to know that we'd be happy to have you stay with us.

Also, if worse comes to worst. In the least favorable situation, if the worst possible outcome occurs. For example, If worst comes to worst and the budget is not approved, the government will shut down, or Go ahead and go to school with a cold; if worse comes to worst the teacher will send you home . This expression is nearly always followed by a solution. [Late 1500s]

If the very worst thing happens.

If the most unfavorable or injurious circumstances should occur. This term would make more sense as if worse comes to worst (comparative to superlative), but it has been used in its present form since the late sixteenth century. It generally is followed by some expedient solution, as in “If worst comes to worst he’ll declare bankruptcy.” The Restoration dramatists had fun with it. John Dryden said (Sir Martin Mar-All, 1667), “If worst comes to the worst, he leaves you an honest woman,” and William Congreve (The Way of the World, 1700) wrote, “If the worst comes to the worst, I’ll turn my wife to grass.”