The answer to the question depends I think on how we define divided opinion/controversy and how we measure it. For example if it's the opinion among laypeople I think Grant comes high on the list, simply because he's one most people have heard of and there's the two simpler schools of thought about him (pro and anti).
Among people who are involved in serious historical discussion it varies depending on time, obviously; I believe that Gettysburg (and The Killer Angels) had a significant impact on the perception of several generals just as one example. Then there's the ones who are written off as a simple story who probably should not be.
I for example think McClellan was much better than most do, but I would not consider him a general who's provoked much controversy or differences of opinion simply because I think the view on him is quite uniform these days (at least among laypeople - among those who study his campaigns it's rather more mixed as far as I can tell). That someone is a cliche of civil war historiography doesn't exactly speak well to him being the subject of controversy, after all.