Close, complex analysis is the second hardest math.
Several Complex variables in two variables is naturally two times as hard as complex analysis, and so on for n variables.
Years ago, Henri Cartan proved that the human mind is completely uncapable of reaching the depths and complexity of five variables, and only the highest of mankind's minds, like Terence Tao, Shinichi Mochizuki and Neil deGrasse Tyson can even begin to do research in 4 variables.
Recently, Witten spent 5% of his brain mass and constructed a model of complex analysis on 4.99999... variables, and he claims it solves String Theory and Quantum skeletons.
