Sounds snarky but it isn't. The best evidence is the preponderance of the evidence. This is not unique to the TOE, of course. It is the norm for all scientific theories.
Having said that, the best evidence AGAINST Intelligent Design and therefore good evidence for the TOE, is the multitude of derived characters we can readily observe as well as a corollary observation, the fact of convergent evolution (different ways of solving the same problem). I am not going to elaborate on the arguments against ID because that would be off topic but if someone wants to propose that topic I will be happy to chime in.