How do you figure that? With four times the population, it's not hard to overwhelm someone with casualties.
Even Mary Lincoln said Grant was a butcher.
Grant used what he had to maximum perfection. His 6 week overland campaign had heavy losses but not nearly as many as if the war had continued. Ultimately he saved lives. Those are the hard decisions a great general must make. And Lee had a higher percentage of casualties. When brilliant tactics were called for he used them. His Vicksburg campaign was the greatest tactical campaign of the war. His whole objective during the Overland campaign was to hold Lees army in place and act as the anvil to Sherman’s hammer. And it completely worked. In every instance he did what was necessary to win.
Even Mary Lincoln said Grant was a butcher.
And yet while Grant and Lee commanded armies for about the same length of time - Grant actually commanded them a few months longer - it was Lee who had the greatest number of total casualties during the war. So who was really the butcher?