>>17926477
Lee's performance against Grant during Overland is actually one of the best examples of his generalship. It's to his credit that he single-handedly prolonged the war for a year by forcing Grant into an attritional siege.
Grant was an excellent attacking general with a good grasp of strategy and knew how to use his superior numbers. Overland was a campaign of maneuver. That it is mainly remembered for desperate brawling in the Wilderness and suicidal charges at Cold Harbour is down to Lee. He countered Grant at every turn, kept his army between him and Richmond, always ensured he faced Grant behind earthworks and solid terrain. Grant didn't beat him in Overland, it was a stalemate. It just so happens that a stalemate wasn't enough for the CSA at that time.
If you want to see Lee's weakness, it was in the wider strategic political sense. He kept telling Jefferson Davis that he couldn't spare any men for the Western theatre which was caving in, and then wasted 15,000 men on a suicidal charge at Gettysburg.