Grant and Lee commanded armies for about the same period of time - Grant from January 1862 to the end of the war and Lee from May 1862 to the end. Lee suffered more men killed and wounded in whole numbers while he commanded the Army of Northern Virginia that Grant did in all his commands.
He also had a habit of claiming his victories and blaming his losses on others.
Examples please?
http://www.civilwarhome.com/casualties.htm
https://www.ben-hur.com/faq/#shiloh
“In General Grant and the Rewriting of History: How the Destruction of William S. Rosecrans Influenced Our Understanding of the Civil War, Frank Varney challenges Ulysses Grant’s widely read Personal Memoirs, especially as they pertain to the wartime performance of Union General William Rosecrans. Varney, an assistant professor of history at Dickinson State University in North Dakota, questions long-held beliefs regarding events involving Grant and Rosecrans in the all-important western theater. While Varney covers a lot of ground in this first volume of a projected two-volume series, the central theme is his contention that, given Grant’s propensity “to make himself look better and blame his errors on others”—coupled with the unwillingness of many historians to challenge “Grant’s veracity”—the general’s flawed version of events has distorted the nation’s understanding of America’s defining conflict (x-xi).
Varney takes a number of well-known Civil War historians—Bruce Catton, Peter Cozzens, Shelby Foote, Lesley J. Gordon, Earl J. Hess, James McPherson, Allen Nevins, Brooks Simpson, and Steven Woodworth, just to name a few—to task for sometimes engaging in lazy scholarship. While some come in for more criticism than others, Varney calls each of them out for a variety of mistakes or errors in judgment, the most egregious of which is falling under the spell of Grant’s Memoirs when drawing conclusions regarding Grant’s successes and Rosecrans’ failures. While Varney’s allegations have some merit, the author’s claims often fall flat in light of his own missteps...
...Aside from these significant criticisms of Varney’s work, he does successfully demonstrate that Grant’s Memoirs need to be treated with the same careful reading as other Civil War memoirs, that Grant and others did sometimes go out of their way to undercut Rosecrans’ accomplishments, and that historians have at times given Grant’s version of events a pass. Again, the central tenet of his book is compelling.”
https://www.civilwarmonitor.com/blogs/varney-general-grant-and-the-rewriting-of-history-2013
https://www.amazon.com/General-Grant-Rewriting-History-Understanding/dp/1611211182