- Sorry for the hype in this answer. But trying to convey how singular - how truly remarkable Ramanujan was, as a mathematician and innovator, is truly difficult without writing a book on him... so please forgive the hype in this answer. I'm trying to give a feel of something that makes hairs stand up on the necks of world class mathematicians even a century later....
Realistically there has never been a physicist equivalent of Ramanujan. Physics requires observation and not just conceptual structures, while mathematics is its own edifice, so to speak.
When you discuss Ramanujan, there are two aspects to his story that are signular - the story of the person (self taught Indian genius who despite this became a world leader in his field), and the story of his capabilities (for example his familiarity with numbers, his almost incomprehensible abilities with arcane and infinite nested formulae, his sheer almost inhuman intuition for a formulaic answer to a problem ...)
There have been self taught physicists who came from non physics backgrounds yet upended the physics world. I am extremely doubtful that there has ever been one - perhaps never will or could be one - who has shown within physics anytning that could be considered reasonably equivalent to the jawdropping capabilities Ramanujan showed within number theory and mathematics.
We are still trying to comprehend how he could work out what he knew, and not merely make use of and develop what he knew and discovered. Even with a century's hindsight he could do things that seem implausible today.
You'd be talking about the kind of person who could develop much of the entire body of modern and near future quantum physics as it stands in 2021 ~ 2040 on the back of an envelope, starting from the knowledge of a 1915 indian villager with a few old textbooks, or something like that, to stand a chance of being equivalent. Maybe modern superconductor theory on the side too. And deduce the masses and charges of bosons that wont be seen for decades or even suspected yet, solving seemingly impossibly tangled quantum wave equations and operator equations (which he also invented or greatly developed) often on pure intuition, seemingly as easily as most physicists can solve school physics problems . and did it all, with the help of some old envelopes for writing out, and a few physics textbooks from 1850-1910, and much of this by age 26.
A Ramanujan would be someone who, in 1920, could be notionally standing in front of Dirac, Schroedinger, Feynman, Wienberg, Higgs and a hundred others (if alive then), and say "It was obviously a group, and it came to me that all but gravity are governed by SU(3) × SU(2) × U(1), including a mass-generating field and mechanism, and it predicts a particle i call a neutron as well as these others I call bosons, quarks, leptons, and their properties and interactions.... ", having also derived or extended the tools needed on the way, such as much of quantum mechanics, quantum field theory, and anything needed on the way as related to groups and operators, including the calculations/arithmetic needed for actual numeric predictions - and then left the sketchiest of densely written notebooks to guide researchers after he died at 32, as to what else he theorised and was working on, and the mathematical and intuitional tools and techniques that had achieved this
That would be a Ramanujan.
I don't think physics works that way, pure and simple.