La penúltima pregunta

La penúltima pregunta
 

In English?
The last but one question ?
Any other possibilities?

Yes: The penultimate question.

If it was the last but two question, you could say the antepenultimate question.

'Last but one', 'last but two', etc. are BrE usages. FYI, here are the AmE equivalents:

ultimate:
the last (question)

penultimate:
the next-to-the-last
the next-to-last
the second-to-the-last
the second-to-last

antepenultimate:
the third-to-the-last
the third-to-last

preantepenultimate:
the fourth-to-the-last
the fourth-to-last

Thanks.