All Might was the #1 hero in his world for a good reason. His abilities are completely off the charts. Endeavor really has no chance in a straight fight. Not only is All Might able to endure his flames but his speed and power means he never has to be hit. He can use wind pressure to keep the flames off of him and then dispatch Endeavor right away. In his prime All Might is just leagues beyond anything his fellow heroes can do. All Might wins.