Question

what is the only one who have been​

Answer 1

first complete your question ---------------

As the sentence stands, it cannot be adjusted purely by grammar to turn it into proper syntax. It could come close if you said, “I’m the only one here who has nothing with which to describe himself.” But nobody would say that. It’s awkward.

I would suggest using “description” as a noun: “I’m the only one here who cannot give a description of (herself/himself).”