Ulysses S. Grant (1822-1885) served as commander in chief of the Union Army during the Civil War and led the North to victory over the Confederacy. Grant later became the eighteenth President of the United States, serving from 1869-77, during which time he did considerably less killing.
After fighting in the Mexican-American War, Grant left the army only to rejoin at the outbreak of the Civil War. Some guys just can't get enough. His victories at Fort Henry, Fort Donelson, Vicksburg, and Chattanooga soon convinced Lincoln to promote him to lead all of the Union armies. You couldn't argue with the man's resume. After a bloody campaign in Virginia, Grant accepted Confederate General Robert E. Lee's surrender on April 9, 1865. He also didn't make Lee do any of that "bow before me" stuff, which was nice of him.
During the Civil War, Grant was the only Union general who could equal Robert E. Lee. (For those who prefer to see everything in mathematical form, Grant = Lee.) Grant's early victories catapulted him into the public eye, and his willingness to be aggressive and fight, two traits seriously lacking in many Union generals, allowed him to keep his post after a near-disaster at Shiloh.
Upon taking command of all Union armies, he embarked on the Overland Campaign of 1864, a brutal war of attrition in which Grant's armies suffered enormous losses as they attacked Lee's on the way to Richmond. Union casualties were so high that Grant was branded "The Butcher." It could also have something to do with the fact that he advertised himself as selling the "best pastrami this side of the Ohio River." Truly, whether you were a Confederate soldier or a cow, you were shaking in your boots when this guy came a-knocking.
After three years of indecisive and timid generalship from others, Lincoln was stoked to finally have an aggressive general to lead his forces against the South. Grant's generous surrender terms at Appomattox Court House helped heal the divided nation by avoiding treason trials and leaving the South with some of its honor intact. It only had to tuck halfof its tail between its legs.
As a not-so-glowing personal recommendation, Grant's subsequent presidency was mired in corruption, and he became caught up in several political scandals. But honestly, what else is new? Politics.