Okay. Let's say that there is nothing--besides a Uchiha with MS, of course--that can counter Tsukuyomi. You have to realize that this is still a genjutsu, which means it is an illusion that occurs for 1-2 seconds. Unless you have a gun, or are Minato or Ay, I don't think there's anything Itachi would be able to do in 1-2 seconds that will kill a formidable opponent, especially after using a taxing jutsu such as Tsukuyomi.
Now, it can be backed up that Ay and Minato, and occasionally Naruto in KM, are the fastest people in the manga, so you can't give some crap excuse that Itachi is capable of using a jutsu--or some physical attack--that will reach his opponent faster than the previously stated three people. It can also be backed that Tsukuyomi is a taxing jutsu, as Itachi has stated it when fighting Kakashi in part 1 and when he fought Sasuke in part 1. Of course, you can state the fact that he could use Amaterasu, but Itachi didn't use Amaterasu immediately after he used his Tsukuyomi on Sasuke. In fact, he had to prepare the jutsu before he used it in the fight with Sasuke. You probably would also use the fact that Tsukuyomi is an exhausting genjutsu on the opponent, which is correct. But even Kakashi didn't have the usual extreme side effects from the genjutsu, which was stated to be an impressive feat.
Now, if Itachi went against a more formidable opponent than Kakashi was in part 1, then I don't think Itachi>any and every character. Realize the truth, dude. Answer this: did Itachi die from the side effects of overusing MS, or was he killed by Sasuke?
PS: answering either of those two questions will prove my point.