What is the most complicated theory in the world?

The big bang theory. well, all theories bc they are theories

Vasiliev theory

Explanation:

Vasiliev theory takes to extremes the basic idea of modern physics: that the world around us consists of fields-the electrical and magnetic fields and a handful of others that represent the known forces of nature and types of matter. Vasiliev theory posits an infinite number of fields. They come in progressively more complicated varieties described by the quantum-mechanical property of spin.

In Vasiliev theory, there are also spin-5/2, spin-3, spin-7/2, spin-4, all the way up. Physicists used to assume that was impossible. These higher-spin fields, being more symmetrical, would imply new laws of nature analogous to the conservation of energy, and no two objects could ever interact without breaking one of those laws. The workings of nature would seize up like an overregulated economy.

the declaration states, “we hold these truths to be self-evident, that all men are created equal, that they are endowed by their creator with certain unalienable rights, that among these are life, liberty, and the pursuit of happiness….”