2 of history’s most famous artists didn’t like each other at all. 2 beloved painters were each asked to create murals on opposing walls in Florence’s Palazzo Vecchio. There’s da Vinci: painter of “The Last Supper” and the “Mona Lisa.” He’s established, revered and confident. In the other corner, the young upstart, Michelangelo: insecure, moody and pious. He’s finished the “David,” but has yet to paint the Sistine Chapel.