12 rounds between 2022-'24 Beterbiev and 1983-'85 Spinks. I'd personally give it to Beterbiev via late-rounds TKO. I think his weight shifts and feint entries, his solid high guard, and his footwork mean Spinks wouldn't be able to control range, prevent longer exchanges, and dominate with counters over the course of the whole bout. Beterbiev knows how to sabotage the gameplan and erode the structure of a faster fighter. He's also too good at layering his offensive over time and accelerating at the right moment.
