(idiomatic) The only remaining, often least desirable, option when all others have been excluded.
I wouldn't recommend doing surgery on yourself, unless it is a last resort.
2020 July 15, “Transport Focus: clear message needed on face coverings”, in Rail, page 9:
"Only as an absolute last resort will we carry out enforcement in the form of fines. We are sure that the public will want to be responsible and do their part to protect others by wearing face coverings."
