Please tell me why my question was closed:
It is obvious that the question is completely concrete (at least in the part of pain) and falls in the topic of metaphysics.
On a neurological forum this would be of course off-topic because the question asks for an answer for any poissible brain construction, not only that based on neurons.
Also as I can tell, theoretical neurology leaves the question about what creatures can experience pain (and qualia in general) to philosophy.
Please re-open this question, I see nothing wrong with it. If it is not suitable for this site then this site is not about philosophy at all.
the maximum possible pain in the universe
is when your question about it is closed.