BoxRec

It doesn't fit the criteria of the question but Larry Holmes had a pretty decent run, most as world champion. Bonecrusher had one defeat, if it wasn't for that Holmes would've beaten 6 unbeaten fighters on the trot. He then lost three times on the spin to undefeated fighters. So a combined record of 176-1-1

Tim Witherspoon 15-0
Scott Frank 20-0-1
Marvis Frazier 10-0
Bonecrusher Smith 14-1 (one defeat I know)
David Bey 14-0
Carl Williams 16-0
Michael Spinks 27-0 (lost)
Michael Spinks 28-0 (lost)
Mike Tyson 32-0 (lost)

margaret thatcher wrote: ↑15 Feb 2020, 22:22 Was looking and saw Josh Taylor beat 3 in a row and it will probably 4 in a row given who his mandatory is.

josh now at 5 in a row and prob 6 with catt next

I remember there was a really hot fighter in the 1980s by the name of Adriano Arreola who beat a string of unbeaten fighters and nearly beat Julio Cesar Chavez in a bruising 10-rounder in 1983.