While the exact percentage of heavyweight boxing champions who fought Southpaw may require extensive record-keeping and analysis, historically, it has been observed that the number of Southpaw heavyweight champions is significantly less than orthodox (right-handed) champions. This is partly due to the fact that Southpaws are less common in the general population, but also because the style of Southpaw fighters can be more challenging for those not accustomed to its tactics.What is roughly the percentage of Heavyweight Boxing champions who fought Southpaw?
Through the history of heavyweight boxing, there have been a handful of Southpaw champions, the most notable probably being Michael Moorer, who in 1994 became the first left-handed fighter to win the heavyweight title. More recent southpaw champions include Charles Martin and Oleksandr Usyk.
So while it's difficult to put an accurate percentage without factual historical data, the percentage is reasonably low. Providing an estimated figure could risk inaccuracies or misconceptions. It's clear, however, that Southpaw champions in heavyweight boxing definitely constitute the minority.