Examples of when a fighter lost to someone they would beat 9 times out of 10, or at least far more often than not.
Max Baer should have beat the crap out of Braddock. He spent a third of the fight smiling, shuffling around, barely putting any weight into his punches. All credit to Braddock for doing what he was supposed to do and executing a good game plan, but Baer's lack of effort was just as much of a factor towards his loss. Braddock was a smaller, unremarkable journeyman with a fairly crappy record. Not particularly athletic, powerful, or fast, and constantly dealt with hand injuries. Just about the only noteworthy qualities he had were a good chin, decent right hand, and a hard work ethic.
I believe Jack Johnson could beat Marvin Hart 9 out of 10 times, especially if he was properly motivated, as in the title on the line (for instance). In their 1 pre-title fight, Marvin got the 20 round win, in a referee's decision fight.
Maxie Rosenbloom lost a couple of fights to guys for walking-around money that he would have beaten 100/100 in title matches. Charley Massera beat him. Probably the best example.
It's easy to pick fights such as Jose Napoles v LC Morgan or Joey Maxim v Curtis Sheppard, because it pretty much really happened. However, I will also go out on a limb here and say Emile Griffith v Hurricane Carter and Eddie Machen v Ingemar Johannson. Like Maxim against Sheppard, IMO. Griffith and Eddie just got caught cold.