מדרש אויף שופטים 1:7

"and you will rule many nations": I might think that you will rule others and others will rule you, as in (Judges 1:7) "And Adoni-bezek said, etc."; it is, therefore, written "and they will not rule you."

We are not told explicitly of the greatness of the Canaanites, but it may be readily inferred from the following (Judges 1:7) "And Adoni-bezek (a Canaanite king) said: 'Seventy kings, their thumbs and big toes cut off used to glean under my table.'" (Devarim, Ibid.) "And they (the descendants of Joseph) are the thousands of Ephraim, and they are the thousands of Menasheh": We are hereby taught that they were blessed with thousands and with ten thousands, viz. (Bamidbar 10:36) "the ten thousands thousands of Israel."