Which Hvy weight Champ Faced A Genuinely Tough Challenger,In His First Defence?

Well, there were only a couple instances when the defending champ was the underdog against his first challenger and lost.

The easiest to predict, because the defending champ was a big underdog, having already lost badly to the challenger previously:

* Frank Bruno (against Mike Tyson in their rematch, as Tyson beat Bruno even easier in their return)

Next, I'd put these defending champs who were underdogs even though they'd never faced the challenger before:

* Jim Braddock (against once-beaten Joe Louis, who was the favorite)
* Trevor Berbick (against undefeated Mike Tyson, who was a big favorite)
* Buster Douglas (against undefeated Evander Holyfield, who was the favorite)
* Bermane Stiverne (against undefeated Deontay Wilder, who was the slight favorite)

These are only lower because the defending champs had already won the first fight, so there was an argument to be made that they'd win again, but were still expected to lose the rematch:

* Leon Spinks (against Muhammad Ali, who was anywhere from a 2-1 to 3-1 favorite to win the rematch)
* Hasim Rahman (against Lennox Lewis, who was the favorite to win the rematch)

This is only lower than the three groupings above because the defending champ was still the slight favorite, not the underdog. So the champ was expected to win, unlike the champs above:

* Ken Norton (Norton was the slight favorite against undefeated Larry Holmes)

This is only lower than the above because the defending champ had already scored a win in the previous meeting and the champ was supposed to win again, but lost:

* Ingemar Johansson (against Patterson, Ingo was a slight favorite over Patterson in fight 2)

These are lower because the defending champs had already won the previous fight, the champs were also the favorites over the challengers, and the champs won:

* Floyd Patterson (against Ingo in '61, rates lower because Floyd was a slight favorite in fight 3, but also rates higher than the two below because Floyd had also lost to Ingo previously)
* Gene Tunney (against Jack Dempsey, rates lower because Tunney already beat him, and Tunney was the betting favorite)
* Oleksandr Usyk (against Anthony Joshua, rates lower because Usyk already beat him, and Usyk was the betting favorite)

 

Nice list.

Side Note: Corrie Sanders wasn't the defending champ against Vitali. Sanders had vacated his WBO belt. Sanders and Vitali were fighting for the vacant WBC belt.

So, I don't think it belongs on a list of first defenses.

 

Tyson fought Smith, right after King Witherspoon in a round, then Thomas a year after being the top fighter in the world, then undefeated Tucker then undefeated Biggs ... crazy at 21 - 22