I've come across some odd questions in my time, but I have to admit that this one is one of the best.
I cannot imagine anyone setting this question for any student regardless of the level of study. I can think of examples in inorganic chemistry, organic chemistry, biochemistry, immunology and many other sub-disciplines that would be good candidates for the answer. There are millions of monomers that would potentially fit the bill and cause immense debate. Leaving aside inorganic chemistry, telling you the answer would only provide you with the name of a meaningless molecule that you couldn't possibly appreciate nor understand. In fact, this question is best suited to a pub quiz as it sounds more like a competition than a genuine question. The same applies to your other post regarding a gas.
Good effort Hyognosis, but I'm afraid that bakelite is very, very far from being the largest organic monomer. It would not be a good candidate even if we confined ourselves to considering monomers taught strictly within University organic chemistry lectures. Like you, I await further information from Sachin114 regarding this question.