What are some examples where Hegel's theory of thesis>antithesis>synthesis>ultimate truth works in practice?
One example where it didm't work is communism.
The thesis was capitalism unrestricted competition. The antithesis was socialism complete cooperation. The synthesis was supposed to be communism. in forced cooperation, leading to ultimate truth, utopia where no government would be required. Everyone would live in peace and equality.
Sadly this utopian dream did not come about. Hegel's theory apparently did not work.
I can not think of any examples where Hegel's theory actually worked.
The Scientific Method is one version of Hegel's Dialectic (which, to be clear, Hegel didn't invent but merely expanded and expounded upon).
Before I dive in on this, be aware that delving into Hegel's philosophy is not simple or easily explained. Here's a prior answer that helps to explain what the terms thesis, antithesis, and synthesis is trying to get to:
This process harkens back to the days of Plato but Hegel added to it to help synthesize more varied and different types of arguments. For way more information on Hegel and Dialectics (this process we're talking about), check this out:
The question before us is Does This Stuff Work In Practice?
The answer I believe is an unqualified yes. Why do I say this? Because as a way of thinking, it creates a process where contradictory information can be processed and utilized to create new, more sophisticated thoughts that in essence negate the original and less sophisticated ones. For example, the methods of exploring using the Scientific Method can be seen as a version of Hegel's work: