Originally Posted by JAIF

Dark Skywalker... don't push it. You've already been warned not to spam. You've actually been suspended for it. It is unwise to test your limits.

We do have Itachi's statement that he would be stronger than Madara if he had the permanent Mangekyou Sharingan. He even implied he was stronger than him in his current state. He wouldn't really say that if he would be defeated by him.