Ramanujan was easily one of the greatest mathematicians in history. Full Stop.
Entirely self-taught, his insights were incredibly novel and have helped human advancement immeasurably. Incredible stories about this great person abound. Sadly, he died at 32 from a curable disease, though misdiagnosed. He was deeply religious, a devout Hindu and vegetarian. His legacy is truly astonishing despite his few years. What he could have accomplished, had he lived, is a tragedy of the first order to mathematics and the human quest for truth.
https://en.wikipedia.org/wiki/Srinivasa_Ramanujan