I gave Shannon a vote.
If there were any points I could raise, they would be:
1. We write "the United Nations Intergovernmental …", and not "the United Nations' Intergovernmental…". We do not use an apostrophe.
2. The verb is the verb to be, embedded in 莫过于。 "最[adjective]的， 莫过于[noun]了" is a standard structure that Nat should learn. The English equivalent would be "Nothing/no one is more [adjective] than [noun]." The "莫过于" is the equivalent of "nothing is more … than". "过于" is the "is more … than". "莫" is the negation. The Chinese verb to be is embedded in "过".
A big caveat: In the final analysis, it is silly and even stupid to try to understand Chinese by means of English grammar. It is as silly as practising football to learn basketball. It is never satisfactory. More often than not it is counter-productive and results in long-term damage. So why are we still giving English answers? We are humouring members who ask for an English answer because the alternative is silence, which is not very helpful, or a Chinese answer that the Asker cannot understand, which is not a very happy alternative either. For any learner, however, the best thing to do must be to learn Chinese without using any other languages as an intermediary tool.