本当に死んでいる....それ以上は一切の言い表しようもないほど....彼女は完全に死んでいた。
My understanding is that 一切の言い表しようもない is a clause inside ほど, but I do not understand what 一切の means. I know that の can sometimes mark the subject in relative clauses but if that was the case would it mean that 一切 or "everything" is the thing that cannot express itself?
This is how I understand this sentence
She's really dead... She has really died and everything cannot explain itself