Hard to go against the Father of the country but Grant helped save it
Washington’s greatest achievement as a general was keeping an Army in the field which alone makes him one of the greatest figures in history. But his greatest triumph over the Brits took a lot of luck and French help.
Grant to your point, pretty much single handed saved the Union and was both a brilliant tactical general and master grand strategist. Lee was former, but not the later.
I never find this to be a fair comparison. Lee seems to not be a grand strategist, but Lee had no real industry supporting him, no Navy to support his field positions, and no railroad of any note to support him from land. I had a lecturer at the National War College once tell me "Lee's grand strategy WAS tactical mastery of specific battles and campaigns." He had no choice. He knew he could not win a long sustained strategic war. It was a "be better than the other guy for like 2 years and kill their will to win, or it's over" strategy.
Lee’s grand strategy of tactical victories worked until it didn’t. Ultimately his jerb was to keep a confederate army in the field until the north lost the political will. He got fucking greedy after Chancellorsville and thought he was invincible and then bet the house at Gettysburg. Major blunder here. Following that he got caught in Grant’s meat grinder and his army withered away.
I do give Lee a tremendous amount of credit for doing the right thing at the end which was to surrender and not go full on VC the hills of Appalachia.
