If he beats everyone in his prime then he shouldn't have needed a rematch. He would've just won the first fight.
To make it clear I'm not saying that Leonard is overrated h2h at welterweight. I am simply saying that he is not unbeatable. Because he lost while in his prime. For example if someone said "Louis in his prime does not lose to single heavyweight in history" You would probably go "Wait a second but the first Schmeling fight proves that he would, because he did." Yes Louis beat Schmeling in a rematch in one of the greatest wins of all time. But the first fight still shows that he can be beaten. Just like how Leonard has one of the greatest wins by making Duran quit but that first fight shows that he's not invincible. There's nothing wrong with having Ray Leonard as your h2h number 1 welterweight. I just have a problem with saying that he beats every single fighter in the divisions history. Because no boxer does. The closest you probably get to that is with Ricardo Lopez at minimumweight but that's because it's a relatively new and historically weak division. I hope that makes sense and I'm sorry if it didn't.
1) SRL fought a very smart fight, frustrating and denying Duran. 2) Duran ate way too many burritos just before the fight ...