Looking for a word or phrase that refers to someone who is unaware of their state, as if they were dead or dreaming but not knowing it. Closest I've come is something like "walking dead"/"dead man walking" or "Dunning-Kruger" but ideally looking for a single word, less idiomatic. E.g., "His inability to execute his work made him into an impotent husk, a [person who is dead or dreaming but does not know it]." The intended use is more metaphorical than literal.
I think you can use the phrase he is as good as dead
As good as dead means he is unfit to do anything and he is almost equal to a dead person.
Here is the link