Robert E. Lee by far. While he was correct he had to win a bttle on the North to shift the balance of the war, he went about it in completely the wrong way. It's worth mentioning that whilema skilped tactician, he proved to an inept strategist. To stake absolutely everything on defending Richmond as opposed to withdrawing southwards and eluding Grant was insanity.
Richmond had the Tredegar Iron Works that were the only way the Confederacy could make munitions. If Richmond fell the war was over.
This is why I find criticism of Lee strange, because without him it's easily imaginable that McClellan captures Richmond in 1862 and the Confederacy disintegrates. The Army of Northern Virginia did its job really, the Confederacy lost because of the collapse of the Western theatre in 1864. It's somewhat unfair in my view to blame Lee for not singlehandedly winning the war (which is what he would have had to have done), and not saving the Confederate army in a different theatre. I think it's important to remember that Lee was a theatre commander, not in charge of Confederate grand strategy, and the blame for the Confederacy's strategic failure has to be laid at the feet of the incompetent CinC Jefferson Davis.
I do accept that Lee is obviously overrated in American mythology, though.