It was Ulysses S Grant, also the 18th President of United States. Fun fact, they both went to West Point and Lee graduated 2nd in his class whereas Grant was an average student at best, but during the civil war, Grant was the better tactician by most accounts and was willing to take heavy losses.
Grant was an alcoholic and his presidency was riddled with corruption and his reputation was damaged by the Lost Cause revisionists after his death, but compared to the other historical figures we regularly call 'great' he is a better person that most of them and I wouldn't think of him as a monster, he was an interesting and complicated chartacter.
Grant was actually a good President; his wife helped him stay sober during his time in office, he probably wasn’t a drunk then.
His reputation was written by his enemies. He worked hard to enforce the 14th amendment, and the south hated him for that much more than the slaughter of the actual war.
Grant was probably a better strategist (or at least he understood his advantages and how to make use of them), but I've never seen it seriously suggested that he was a brilliant tactician. Relentless might be the best description of Grant. There's very little brilliance in the Overland Campaign of 1864; the primary thing that set Grant apart was that he continued pressing on after being bloodied, rather than scurrying back to Washington, feeding men into the meat grinder knowing that he could trade bodies for far longer than Lee could.
I agree with the north's advantage being in numbers and resources, but I think it's more complicated than him trying to batter down Lee with it. This image of Grant throwing lives away needlessly comes from the Overland campaign in the war, and it was a complex situation with both of them probing for advantage and Grant eventually pushing him into a siege. Lee lost initiative and wasn't able to recover from that. Sherman, another Union General was able to go into the deep south after that and destroy the south's ability to fight leading to a surrender. I think strategically, he was able to out-perform Lee which no other Union general was able to do in the civil war, which was pretty different from how wars were fought up until that point.
Comments on this post lays it out in much more detail.
I didn't say he was a monster. I said he was considered to be at the time that he was General during the Civil War. I chose that wording carefully.
In a nutshell, my understanding of the war is that Lee was a brilliant strategist and tactician and the primary advantage the North had was numbers of soldiers. Grant did not hesitate to use the only advantage he had, resulting in a high number of deaths to gain the upper hand. Lincoln had his back politically and did not replace him. Lincoln apparently believed in him.
Sorry, I wasn't trying to imply you called him a monster. I was agreeing with you that he was a brilliant wartime soldier and fared poorly in almost all other areas of life, but as a person he gets treated a bit unfairly by some historians.
Grant was an alcoholic and his presidency was riddled with corruption and his reputation was damaged by the Lost Cause revisionists after his death, but compared to the other historical figures we regularly call 'great' he is a better person that most of them and I wouldn't think of him as a monster, he was an interesting and complicated chartacter.
Source: https://www.amazon.com/Grant-Ron-Chernow/dp/159420487X