The best Lee could manage at Sharpsburg was survival, and it was less due to his own efforts and more due to the failures of McClellan and the initiative of Lee's subordinates (like Jackson and A. P. Hill). At Chancellorsville, Lee made one good move that succeeded in spite of all conventional military wisdom (and conventional military wisdom is usually right) and then spent the rest of the battle engaging in unimaginative and foolishly costly attacks on a perimeter that was only abandoned due to Federal command incompetence. And at Gettysburg, he absolutely was outgeneraled in that he chose to fight there under unfavorable circumstances and in so doing made the incorrect decision.
Lee was certainly an adept general officer in some respects, but he left a lot to be desired in tactical terms, not just strategic.
At Sharpsburg, just surviving was about all you can expect to get when youre caught looking the other way during a snatch n grab raid and two major elements of your army are not around. At Chancellorsville while yes after a miraculous start Lee didnt get much done, but he still called out Hooker as even more inactive than Little Mac. And his rearguard action defending against Sedgwick from Fredericksburg at the close of the battle was impressive too.
Gettysburg was not his choice, it was chosen for him. July 1st, the armies have already started engaging. If Lee wanted to try and go back the way he came than his forces would have gotten even more separated and have gone deeper north, making the possibility of getting cut off more real. If you want to go south, you have to go through the Union army or expose yourself to flanking attacks. There was almost nothing Lee could have done to avoid Gettysburg.
Seven Days' Battles. If you want a single specific one, Malvern Hill. You've seen the ground there. An attack over that against the fortified Federal position was lunacy, and the hemorrhaging the ANV sustained was commensurate with the stupidity of the assault.
A) Seven Days was his first battle in command of the ANV. The only reason that he was put in charge was because Johnston was wounded and Lee was sitting in the War Office twiddling his thumbs. He was thrown into a situation with officers and staff he hadnt worked with before and an army in retreat.
B) He still won the Seven Days. Knowing your enemy, hounding him, freaking him out; these things he did masterfully well here. Yes, he went a little gung hoe in the attack department, but he was close a number of times in cutting the Union army in half. Its a testament to the Union army that they held.
C) The question at hand was if there was a case where his wasting of manpower almost lost him the battle, in the Seven Days battles he was never really in a position to lose. Most of the battles were attempts to make the most out of a Union retreat already in progress.
Correct, but it was incompetently executed, partially due to the failings of Lee's own subordinates and partially due to Lee's own failings. That reflects badly on his generalship.
Never said he was perfect, in fact I have often said otherwise. But again, the question of debate is if he lost because of manpower misuse. He didnt here, if anything it was a good allocation of manpower executed poorly.