pain, insupportable, intolerable, acute, unbearable, agonising, unsupportable, chapped, achy, angry, chronic, crippling, impossible, agonizing, insupportable, bad, extreme, insufferable, unsufferable, burning.

So long as we are not absolutely certain that Blanche is your lawful wife, the position is more than serious: it is unendurable. - "Man and Wife", Wilkie Collins.

At eighteen she would be unendurable. - "Together", Robert Herrick (1868-1938).

It puts her in an unendurable position to have to defend such a person. - "The Title Market", Emily Post.

unenviable, unexcitable, unerasable, uneatable, unexpendable.